Yep, wood ashes work great (from a wood burning stove or a brush burn pile). Make your birds a tempting dust bath of sand and wood ash, and maybe some peat moss in their pen, run or free range area that they will use daily... they will dust themselves and you won't have to. Or if you want to use a less natural, and possibly more effective/preventative you can sprinkle a dusting of Sevin dust (garden dust for bug control on veggies) on the coop and run floor before you put down new bedding. Neem oil on the roosts works good for mite infestations (mites hide in all the little cracks and crevices during the day then get on the birds at night, but lice are on the birds and in the bedding usually 24/7). I find that an ash dust bathing spot keeps all of my birds mite and lice free all yr long tho.
IMO, Diatomaceous Earth (DE) is a waste of time. It's dangerous to breathe (even food grade) for both you and the birds, and it does nothing inside the bird once it's wet in the gut. It does have a useful purpose for controlling weevils in dry poultry feeds, but that's about the extent of it.
