I have food grade DE and have been using it in their loft area of the chicken ark. I don't know how much DE to use, but I've been sprinkling it around with a stainless steel shaker fitted with a mesh/sifting top cap. I purchased it at a kitchen store.
It is down in their lower run area that I wanted to build/put a dust bath area. The ark is moved around our yard and placed on to fresh lawn every couple of weeks so I wanted to provide them a really nice, proper dust bath area.
I like the idea of play sand. Where do you purchase it? Wal Mart, farmer's supply store or elsewhere? How much DE would you add to say a cat litter pan size of sand?