My method, works in 24 - 48 hours.
Fold a business card in half, preferably not one that's glossy or coated.
Take a single square of toilet tissue. Fold it in half as many times until it will fit inside the folded business card. Do not put TP in the folded business card yet.
Run folded TP under water for a second, remove, press with index finger and thumb so it is not dripping. It should be moist, but not sopping, and certainly not too dry.
Now you can place moistened TP square in business card, put this little parcel on the top of a tobacco in a tin or a jar. Seal with lid. Tin may need to go inside a ziploc bag to ensure moisture isn't migrating. Larger jars may need two of these. Do not fret if tobacco stains the card slightly.
Wait 24 - 48 hours.
Some tips: Index cards make great surrogates, but stiff paper stock. It keeps the moisture away from the tobacco without a fuss. Do not leave any packets in the tobacco for more than 48 hours; mold may develop. If more moisture is needed, repeat process with fresh packets, and add more packets.
Living in the desert, I have this problem a lot. I discovered this method because I got tired of relying on finding those damn clay discs whenever I needed them, and after a while, the discs do fart out and stop soaking up the necessary amounts of water. I also about had a psychotic episode trying to get the "steam bath" method with all sorts of bowls, plastic, towels, hot water to work without soaking the tobacco in condensate or due my own clumsiness. There had to be an easier way, and I found one. It turns out dry tobacco is naturally hygroscopic, more so than moist paper. Paper traps all minerals and other undesirables. Disturbingly cheap, readily-available, nearly foolproof, easy, and disposable (though I can and do re-use packets once or twice if they're not too stained).
Happy hydrating.
8)