I got a 50 lb bag of DE and every week or so I dust all the coops, straw bedding, all around the dogs, everywhere. You can dust the birds themselves too, but I can't say my geese have ever had the same kind of problems that the chickens can. I think because they bathe every day they they don't attract mites. (?)
I'm new to geese, but my ducks have never had a problem with mites/lice like chickens can. I have read that it is because they spend so much time in the water.
You do have to be careful with DE. It's mostly made up of the glass-like (silica) cell wall of little plankton called diatoms and will definitely cause damage to lungs. I have some, but I don't really like to use it either for that reason.I am scared of that stuff... It is crushed... powdered shells...it slices and dices.. sounds fine when it comes to killing bugs.. but I don't want it in my lungs....That stuff doesn't go away.