I'm assuming you mean bark like Repti_Bark, etc?
Easiest way to clean it, is scoop the poop out, then take the bark and wash it. Let it air dry, or bake it to dry it, and you're all set.
( I HIGHLY recommend baking ReptiBark before using it, because it's a common problem, that it has wood mites in it, which can be a pain in the butt. Personally, I now bake any new substrate I get after having to deal with the wood mites.)