Personally, I use and recommend orchid bark, as it holds moisture better (I live in a dryer area than most) and I seldom have any issues with bedding stuck in the mouth. The few times I've seen bedding in my snakes' mouths, they're easily able to wipe it off themselves.

Some folks prefer paper or papertowel, which are also options, but I find scooping out a small corner of dirty bedding easier than completely swapping out all the paper in the cage. It's definitely a matter of personal preference.

-Jen