Be careful with the DE is is a respiratory irritant. You don't want them inhaling clouds and clouds of the stuff. If you are shuffling stuff around making a poof cloud with DE, let it settle before letting them back in.
It works in the cracks and crevices too, around the floors, where they bugs can run through it, it gets on them, then kills them for the most part. I actually put a small amount in their food once a month, I hear it helps for worming, though some here say that's useless. I have seen their combs change from pale, to bright healthy read after DE food, so I want to tend to believe, it does help somewhat from what I have see. Putting some outside may help too, get the bugs BEFORE they get in, but depending on your situation if it's just going to turn into a mud pie, then that'd be just a waste.
Aaron