I put DE in with the sand and sweet PDZ. During a long rain spell the sand got damp so I put in a separate dust bath pan. They used it initially but then just marched around with it. I left it in for a while anyway. But I have fixed a drainage problem from the roof that was letting water run into the coop, sand is mostly dry. They dust bathe where ever they choose.
In an answer to another question in this thread, I throw scratch in right on the sand. They will peck around and forage in the sand anyway so I throw scratch in every morning before work. I leave very early, it's still dark so when they wake up they have something to forage around for. Once a week I rake and scoop and mix up the sand. I've discovered that stinky wetness and odor gets trapped on the bottom while the surface is clean and dry. This I'm sure is because of the concrete slab e the coop is on. It doesn't drain. First time I discovered that I was horrified by the smell I had uncovered. Now that I stir and mice once a week I don't have problems. I remove wasted food, cabbage leaves ect. It's all working for me. Everyone's situation is different so, what works for me may not work for someone else.