The wood ash helps as a preventative for mites/lice when they bathe in It regularly. To treat the parasites it does nothing. Sevin dust powder can be found in a hardware store. Can be in a 3 pack under 10 dollars. A container can do a bunch of birds besides the run and coop. The Sevin dust is one of the cheapest ways to handle mites and lice I have found. Diatomaceous Earth though natural does not work.
All bedding, nesting material will have to be removed and disposed. Sprinkle in coop, run, all cracks, mix in areas they bathe. To do hens sprinkle on them while wearing gloves and a mask. Be careful not to make a cloud of the powder, working it down to the skin. You can also use an empty feed bag with the powder inside. Place bird in holding bag around the neck and work the powder in by holding her and slightly shaking and work the powder in through the outside of the bag. (Shake & bake) That can be stressful and bird will freak causing a big cloud of the dust. To apply around the head I use an old paint brush to dust the head, wattles and comb be careful to not have the hen breath the dust. After treatment of all birds, make sure you wash all your clothing and shower to remove any that may have gotten on you. You need to repeat in 7-10 days to get any that may have hatched.
You will have enough to treat again in 6 months or when reinfested. Getting on a parasite internal and external control schedule is a good plan. Good luck hope that was helpful.
