I just mixed up a dust bath that my girls are crazy about. Because I couldn't find the exact proportions here (although I know I read about them somewhere here or on a link from someone's post), I just eyeballed it.
I started with some peat moss (which was kind of moist, strangely enough) and added some red lake earth that I'd brought back from the feed store (it's supposed to be DE with some kind of clay), then I sifted some wood ash from the stove (yikes that stuff is dusty) and added a couple of cups of food grade DE that I'd ordered online. It all still seemed too heavy to me, and then I remembered that the chickens were taking a dust bath in the brand new shavings when we first brought them home - so I added some pine shavings and kept mixing it all up until it seemed like it would be light enough to fluff around in. Oh, and I mixed it in one of those low black tubs from the hardware store that you use to mix mortar and things like that in.
On day one: they didn't even look at it and I was so disappointed. They just kept bathing in the dirt by the back porch. Day two: one of them started eating stuff out of the dirt bath - and I thought she must be crazy. Day three: they found it. Yippee! Our own grimy dirt bath!! There's still a big pile of dust on one of the roosts because someone went to bed and shook all the dust out of her feathers. It's fun to watch them burrow and wiggle in there. It's amazing how they're able to grind the back of their neck into the dirt and get it all the way up under their wings. Even the babies are in there when their mom is using it. So cute.