It seems the Atlanta botanical garden mix is a staple, and people just sort of take it and make it their own. Their mix is as follows:
2 parts fine fir bark
2 parts fine tree fern fiber
2 parts milled sphagnum moss
1 part fine charcoal
1 part peat moss
Coconut fiber is fine to use in the mix, as it breaks down very slowly and holds water nicely. As for misting, it depends on the plants. Most plants I keep enjoy the humidity, but it is more a requirement for the frogs. I mist twice daily, but you probably wouldn't have to do this simply for the plants.
Too bad about the tree frogs, I bet there's lots of people here that would love to have such a problem, haha.