Im sorry if this is a dumb question? My hens come up to the side on my house and dig a little hole in the sandy dirt, then they take turns, sitting in it and flapping there wings. They cover themself in sandy dirt! So do I need a dusting box? How big should it be? What do I put in it. I dont want them to look dirty like they do now. 3 of them are fat Lt. Brahmas that can bearly fit in the nesting boxes. Please help. Thanks for the help with my crazy chickens and my huddy will be happy when they stop making holes beside our house foundation.