I'm behind, and I don't know if this got mentioned, but I've been testing this product and absolutely love it so far: 4-pack: Humidipak 62%
They recently came out with this particular RH level specifically for MMJ. You still need to do a proper dry to get it close, but once you get it close these will keep it at 62%RH, which is ideal as I understand it (that was their conclusion as well). I had a jar that had over-dried, and it re-moisturized it. I put one or two of these little packs in every jar I have, and so far they work great. If it gets too humid, it lowers the humidity, if it gets too dry, it raises it to keep it at an ideal moisture level. Perfect for keeping things fresh and at correct RH for extended periods. These things are no brainers for me now! Also, this link seems pricey to me. I think I got these things at the local headshop for 50 cents each if I remember correctly. Maybe a buck. You should have seen the look on the guys face when he told me you only needed one or two for a good size mason jar, and I said "okay give me 20 please". Haha!! They have these in other RH levels, too, but my understanding is the 62% is the one to get for MMJ. The higher RH's are probably better for cigars...
I did some digging and researching and have been testing these - I really think they're a great deal. Like I said though, it's no substitute for proper drying first. You've got to get it "close", first.