Do you keep a separate area for this?
I made one and I feel they never use it. So I just sprinkle Wood Ash and DE in their coop and mix it in with their wood chips. They prefer making their own dust bath areas
Mine have a spot in part of the run under the coop that stays dry, they use that if the rest of run is too wet. But they have random dusting spots all over. Anytime I added ash or other things, they avoided it.
I do not. Mine have access to the ground and make their own dusty bath areas. I do not add DE or ashes. I add nothing, just let them manage it the way chickens with access to dirt have been managing it for thousands of years. Why waste my time and energy and raise my stress levels when they do their own thing anyway by trying to micromanage something they can easily handle.
If your facilities are such that they don't have decent access to dirt where they can manage it, adding some type of dust bath area might be a good thing. I don't have experience doing that so listen to people that do.