Flicking water drops works for me. You can use distilled water. Or not.
If the tobacco is super dry, lay it out on a counter or paper towel and flick water all over it. Don't soak it, but think about how much water do you need to get all that tobacco rehydrated? And then do a little bit less. Bunch it all up and put it back in the mason jar and let it sit in a cool dark place for a week.
Tobacco is dried and hydrated and dried and hydrated several times before it comes to market. It's not rocket science, and it can get moldy, but that's the way it goes.
Once a week opening up and check it out and see if it's properly hydrated. Adjust accordingly until you think you're going it just right. And then let it sit for a month or two. Sealed. And then start to enjoy.
Should be fine