I have tried carpet (back when I didn't know better), eco-earth (now there's some mold), cypress (just didn't like those big sharp pieces), and newsprint and have finally landed on aspen as preferred substrate.

I use Aspen on all snakes and rodents, and have never yet had a mold problem. As long as you clean up wet spots and fluff it every now and then, there shouldn't be a problem. It's cheap, soft, nice looking, easy to spot clean, and when you put a layer of paper under it a total clean up is a snap! Just roll and toss.

I, too, feed my BP in a different enclosure, but that's mostly because her cage is really really busy. The corns eat in their cages with no trouble.