I mist with hot tap water, once the water is sprayed it gets cooled in the air. I doubt you'd send a gtp into thermal shock although small neos could experience a drop in temp from it owing to their small mass. If I don't heat the water first they flinch when they get misted, hot water they don't flinch as the mist only drops to room temp by the time it hits them. I don't think it's absolutely
necessary but I think they prefer it. If they are happy, I'm happy.
I don't like misting systems very much, If you've got loads of greens I do see the point but I prefer to do it by hand and I think it's a good opportunity to get a quick look at them and check their welfare while I mist. I don't mist everyday, some days I mist a little more than others, it depends on the weather and the conditions of the snake and enclosure at the time, misting systems don't have that kind of judgement.
A wet enclosure doesn't always equal a humid enclosure either but it can equal water blisters. Rather then spraying every day I scatter a few handfuls of damp sphagnum moss in the tubs of my older greens. When the moss comes in contact with heat the moisture in it evaporates and maintains a humid but not dripping wet environment. I also use the moss as an indicator of how much I should be misting, if the moss starts to dry out completely I know it's time to spray a little more. I can noticeably feel some of the humidity in the enclosure when I reach my hand in there but nothing is dripping water. Greens are tropical, not aquatic lol.
I also inject water into their food before I offer it. I've only started doing this recently as it was suggested by a breeder I respect a lot (and was also the source of my first gtp hatchy and consequent gtp addiction) I can honestly say my older greens have never looked better. I've never had shedding problems or anything before but the shine on my greens now is unbelievable.
As far as weird and wonderful inventions or innovations I don't have anything to offer but if you're looking for a way to increase hydration, I'd recommend looking into water injection