Foil treating the screen top or getting a well-fit plexiglass piece are the best ways to keep temps and humidity up in a tank. I have a picture tutorial on how to put on the foil if you'd like me to PM it to you.

Once you foil treat, and add insulation to the back and sides of the tank, the temp and humidity should be fairly stable. You may still have to add a moist hide during shed times, but you shouldn't have to mist much at all.

Reptibark and the coconut fiber stuff aren't the best beddings. The coconut stuff is messy and molds easily, and the reptibark isn't really very soft and can mold as well.
The best bedding, IMHO, is aspen. It keeps humidity but hardly ever molds unless soaked, looks nice, and doesn't cost a lot.