I've tried all the ways known to mankind regarding rehydrating tobacco because I love smoking old tobacco that I otherwise never would have gotten a shot at in the good old days. I'm really not sure that one way is better than any other. If the tobacco is rock solid but dry, I just pack the pipe as I normally would and then put my mouth over the top of the bowl and slowly breathe down through the bowl and stem. One or two breaths like that usually perfectly rehydrates the tobacco.
But for super dry tobacco, (and only do this with a full tin), I just take a paper towel, soak it in distilled water, wring it out as hard as I can with my hands, spread it out, put no more than 2 ounces of tobacco in the center of the paper towel, wrap it back up over the tobacco and put it in a mason jar. Seal the jar and wait 24 hours. Then, simply open the paper towel and put the contents in the Mason jar. The tobacco should be perfectly rehumidified. If it is a little too moist, just leave it in the jar with the lid off for a couple of hours and that should get the tobacco just about right. It's sort of a trial and error thing, but after a short while, you will get a good feel for it. Hope this helps.