I just discovered this stuff because we picked up a Viper Boa and needed to raise the humidity substantially (75%-90%). I made a moss box/humid hide with this stuff...I mixed about 90% moss with 10% substrate, and sprayed it down nice and wet. Holds moisture much better than standard substrate alone (probably 3x as long).
Next, I am going to mix maybe 30% moss and 70% substrate (small bark) and spray it daily. This shhould work out fairly well I think.
For use as a nesting material, I'd say spray it down just a little to weigh it down. My Viper Boa adores the stuff.