Probably because I just saw the post. I have been very sporadic on here lately because i have had more duties at work. It comes with going from a teacher assistant to a full fledged special education teacher!
I buy bags of DE at TSC. It's food grade with the cow feed. I mix it equally with play sand and wood ash. I used the mix in 1/2 of my coops this year. I had no mite problems in those coops at all.
I also took to sprinklings variety of aromatic herbs in the coops and nesting boxes. The herbs are supposed to keep pests away also.
I made a dust bin with 2x4's for just that purpose. I dump stuff in the bin including insoluble grit. The must like it cuz it's always used. I forget to use the herbs though. What kind do you use?
I've planted Spearmint around the runs too. It give a good smell when I hit it with the mower. Clears the sinuses too.

I remember folks used to use herbs to keep mealy moths out of the flour/grains.
I also use DE in my can of Scratch grains. No more moths. You should use it with your bird seed too if you have a feeder.