During a shed I actually soak the moss and put it in dripping wet. Then I just mist it to keep it damp. When not in shed I will sometimes soak it and then let it dry out and other times I will just give it a good spray.
The cheap bottles are fine. I just found that they didn't last that long and really just frustrated the hell out of me when they start to mess up. They certainly can work though. That nice one I bought is a dream though and I should have bought it sooner.