looking forward to see the answers  😎 

I usually put the tobacco in a jar if it’s not already. I then take a paper towel and get it soaking wet, then squeeze it out to the point where no water drips from it, then fold it and drape it over the top of the jar, not touching the tobacco and then set the jar lid on top, not screwed on, but just resting on the paper towel. I wait about four to five hours and check it. I will usually toss the tobacco around and put the paper towel back on, re-wetting it if it’s dried. 

I check the moisture level by squeezing the tobacco and I pick where I want it to be from experience. I will note that if you get tobacco juice or brown marks on your fingers when you squeeze it, it’s definitely too damp and needs to be allowed to dry with the jar open. 

When it’s where I want it, I throw the paper towel away and seal the jar and let it sit for a day to balance the moisture in the jar and check it again. 

When I first started smoking, a number of people I knew back then would cut a wedge of an apple and stick it in the tobacco jar to re-humidify it. Works great but does give a tiny hint of apple flavor to the tobacco. Not necessarily a bad thing.

I haven’t needed to do it so far, but I’ve heard of people putting a wedge of potato in the jar. It supposed to rehydrate the tobacco without imparting any flavour to it.

Edit: a peeled potato wedge, so no soil gets in the jar.

I use two methods.

1-Towell method. Extend the tobacco in a well cleaned Pyrex roasting pan or a similar tray large enough to extend the tobacco. Wet a very clean towel and squeeze it to the point that no drop of water will scape from it. Put the towel over the pan with care avoiding any contact with tobacco. Check after 3 - 4 hours. If the humidity level is to your liking, transfer the tobacco to a jar.

2-Clay Cookie method. You can find inexpensive clay cookies in every serious tobacconist. Drop the cookie in a glass with mineral water for 5 minutes. take the cookie and dry the excess of water with kitchen paper. Put the clay cookie in the tobacco jar into the tobacco. Wait 2 - 3 hours and hand remove all the tobacco in the jar to check humidity. Repeat process if necessary.

Do not wait to the tobacco is completely dry to rehydrate, because if completely dry, tobacco can lost the oils responsible of the flavor.

Those are a lot of very helpful answers. Thank you all.

Ideal humidity range? I know for my vintage Martin guitar it's between 45% and 65%, so that's what my tobacco gets whether it wants it or not. (ha, ha - They're stored in the same humidity-controlled room). But, that's when I'm "setting it out to dry" - and most blends usually dry out some while sitting there -  looking gorgeous and promising good things with their aroma - breathing the same air with me before I pack them. So, I'm going to venture a guess that the ideal humidity is at least 5% higher than the ambient humidity. So, my scientific wild-ass guess is 70%  (you can quote me if you want - ha, ha). I honestly have no clue. Somebody correct me if I'm wrong.

Different by Blend? I would assume so. Some aromatics need to be moist to do their thing well - part of why they're so finnicky. On the other extreme, I've found (in my narrow experience, mind you) pure Virginias do their thing best when drier (not dry) - the sun-dried hay, fresh mown grass and baked bread flavors and all. Once again, only an educated guess. Would be glad to learn a better answer.

How do I re-moisten? Very seldom need to because I transfer blends bought in bulk to Mason Jars immediately. Same with tins that don't reseal airtight. Three creative methods I've used (not already mentioned above by more experienced brethren of the briar) are:

Creative rescue #1: (My Green River Vanilla rescue story) Back in 2013-2014, I took up the pipe for awhile before losing interest. I packed away my remaining open tobacco in quart mason jars with plastic twist-on lids - until I took the hobby up again just this past Summer - and discovered those plastic lids had lost their airtight seal somewhere along the way. I had A LOT of Cornell & Diehl's Green River Vanilla (my 3rd favorite back then, behind Trout Stream and Milan's Sunset Rum). Anyway, the other aromatics had enough humectant in their recipe to still smoke fine after ten years in leaky jars. The Green River? eh, not so much 😕 Two full quart jars of Kentucky's finest Burley became Kentucky's driest cardboard. No spring-back when pressed down in the jar. No aroma. No flavor. Before tossing them, I figured I had nothing to lose in attempting some CPR (creative pizzazz resuscitation). So, I moved them to fresh KILNER jars (with wire-clasped glass lids - I learned my lesson). And... I baptized them in booze! Yup! For one, I chose Plantation Original Double Aged Dark Rum - the rum/vanilla combo is a natural match. The other got a pure Kentucky treatment - Black Ridge Special Reserve Port Barrel Finished Straight Kentucky Bourbon - which slapped that Kentucky Burley right back to life and then some. I used a graduated jigger to measure 15ml shots, adding a shot, sealing the jar and waiting a week, then press-testing the "spring" and feel, then adding more. After two or three weeks, they were better than new! And, now I have two custom-infused, 10-year-aged Green River Vanilla blends that are pretty amazing for what they are (not my favorite anymore as my palate is developing).

Creative rescue #2: (Fading Frog) Another of those leaky jars had nearly 100g of McClelland's "Frog Morton's Cellar". Imagine my dismay when I discovered this irreplaceable treasure was a ghost of it's former self - not bone dry, but dry. Well, it just so happens there's a cube of charred oak whiskey barrel stave that comes inside the tin - and I saved it. You can guess what comes next - it saved the Frog Morton. I simply repeated exactly what McClelland did when they put a wet stave in the tin when packaging. Well, not exactly. I dribbled a few ml of my favorite RYE WHISKEY on the charred side of the stave after wetting the whole thing in distilled water. Then I buried it in the center of the tobacco. I continue to use the stave and distilled water to gradually raise the moisture level as needed. Whiskey barrel sponge to the rescue!

Creative rescue #3: (the law of averages) Finally, I over-reacted to a bad experience with a really wet plug by way over-drying a batch of 12g of it (sliced thin, rubbing out well, then dried overnight on a tray). I was determined NOT to ever smoke it wet again. Well, I had turned into raisin bran without the raisins. The fix was simple. I sliced and rubbed out 12g more of the "too-wet" bar and mixed it with the "too-dry" stuff in the same sealed jar. Presto. Just right. 

I do find that dried tobacco loses quite a bit of its luster and ends up more bitey after rehumidification, but I am a stubborn man and I don't let any tobacco go to waste. 

I do not like aromatics, but this method I imagined yesterday can work. I didn´t tried it, but I´ll do.

Put your dry tobacco extended in a metal grille like those used to prevent insects from entering home.

Take a cooking pot and boil the essence you like better, Vanilla sticks, or a liquor of your choice, for example. Put the metal grille over the pot and the aroma filled vapor will moisten the tobacco and impregnate it with the chosen aroma. 

When the tobacco is wet and hot, press it with a heavy object and let dry to your liking. 

If the tobacco is dry and spoiled this can give it a new life, or maybe not, but you'll enjoy the process.

Try throwing a little piece of orange peel or apple peel in with your tobacco. I've tried it and it does rehydrate it. When the peel dries out, toss it and put a fresh one in there to keep it hydrated.

Recently i got a few small "bags" of 62% BOVEDA.
Do you guys have used it? What could be the best humidity grade to put inside the jar together with the tobacco?

A word of caution on using fruit to add moisture to your tobacco. Fruit turns moldy and mold will ruin your tobacco.

I have read about this nightmare and have avoided any fruit for tobacco.

Use distilled water on a paper towel.

Just my two cents.

Lager

I will add a point that I never hydrate tobacco unless I’m opening a really old tin or package that is truly bone dry. If it’s got some moisture, I’ll probably still allow what I’m going to pack in a bowl dry a little beforehand. I never have tobacco dry out while stored in a canning jar so I don’t feel the need to do it often. Also, even when I do open a package of really dry tobacco, I smoke some as it is to see if I like it that way before I rehydrate. I find some tobacco smokes the best when really dry. 

说真的朋友，我认为不同品牌的烟草有不同的口味调教，每一款烟草出场的湿度都是不一样的，但我打开一罐新烟草，我会立即装进密封罐中，

但是，如果要加湿，记得用蒸溜水+纸巾，切记，别让他们和烟草接触

祝你抽烟愉快！

Just trying out purified water on a paper towel with some Captain Morgans Spiced Gold rum added for good measure! Trying it out on an old Schippers Tabak packet which was unopened from back in 2015, so it's a little dry... 

I have a few odds and end jars that I negligently didn't reseal the lid on after opening. Bone dry. 

Here's my rehydration station. Just an airtight container and a small clean jar full of distilled water. This is all latikia heavy stuff. Star Of the East and Lancer's. I probably should do the separately but they're both late bombs so I don't gaf. I'll just do it by feel. I have hygrometers but I know when pipe tobacco is right. 

I'll add that you can buy humidity beads real cheap. 

When I was buying a lot of cigars I had 3 coolidors I kept stable for years with a women's nylon full of beads. I'd just run filtered tap water over them when they started to feel dry. Stayed locked in at 68%.