For red mites, I used a standard garden pump sprayer with pyganic specialty, cleaned their whole coop, sprayed their whole coop inside and out, the ground around and under it, and let dry for a bit, and then when they were on the roost at night, I sprayed all their roosts again and legs and bellies. Then I waited a day. Then when they came out in the morning, I sprayed their backs and wings. It was easy to do when they were eating their treats in the morning. I did this again every 3 or 4 days for a total of 3 applications just to be sure. Then I monitored to see if there were any problem areas left. I applied DE super thick to all cracks for prevention and to catch any stragglers who may be fiending for blood.
You can also use a spray bottle as mentioned, but if its a bad infestation or a large area, the pump sprayer works perfectly and goes much quicker. You can also adjust the nozzle to get a fine mist on the birds, and a thicker spray on the coop and in the cracks.
I did try neem before this and normally that works fine for a very mild infestation or spot treatment, but does not work well in heavy infestations. There is a Safer brand neem RTU that comes in a spray bottle, if you only have a few birds you are treating. When I used that, I basically ran out right away, as I have 30+ Good Luck!
