Long answer to a short question...
I have found that the plastic rubbermaids do a much better job of holding in moisture than a glass, open top viv. I have one male in glass and he consistently has problems shedding. I have found that covering part of the screen top with newspaper helps retain more moisture.
With the Repti-Bark, you can mist the bark with a little bit of water. Not enough to soak it, just enough to add trace moisture. I use Repti-Bark in a rack system and sometimes have drinking water spill when I remove the tub. I clean as needed and then mix up the bark, absorbing the water. The rule of thumb I use is place my hand in the bark. You shouldn't be able to actually feel any wet spots. This works pretty well and keeps the humidity consistent. I have never had a problem with the snakes shedding using this method.
As a side note: The climate you live in plays a big role. I live in the Southeast part of Texas, where humidity is high year round. You don't want to increase the moisture to a level that can cause health problems for the snake.
Hope this helps.