On a short-term basis, the best method is to pack your pipe and breathe through it, moistening the tobacco with your breath. It's surprisingly effective.
Do not directly apply water to the tobacco. It works for a short time, but can lead to molding. Of you have a tin, take a couple squares of toilet paper, folding it in half over and over until you can't fold again. Wet it, ideally with distilled water, then squeeze out all of the excess water. Fold a business card on half and put the TP square inside the card, then seal it in the tin and wait. Very reliable.
For larger quantities, I use silicon cigar humidification beads. They're very inexpensive. Hydrate a small quantity in distilled water in a jar. Enough to make about a cup. Place it in an open glass jar. Put the jar and the tobacco in a plastic bag, close it up, and wait a week. Of course, keto the tobacco out of direct contact with the beads.
Prestige Import Group Crystal Gel Humidification Beads for Humidors - 4 oz Bag
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