Hi guys, new chicken mom here.i have two silkies babies- 4 months old. Just learned about dusting. I currently have on hand topsoil, sand from the beach of california, and diatomaceous earth food grade extra fine. How much of each if at all do I put into a tub and do I need to add anything else. I read about wood ash but I can't find it anywhere and don't have access to it. Any help would be the best. Thank you!