Do you have any gaps between the wood in your coop? I know the mites like to hide in the gaps, maybe some of them are hiding & the spray is not getting to them? I have lots of gaps between the boards in my coop so I am going to paint it & try to seal up the gaps. BTW we gave our hens a flea bath last weekend & are going to repeat next weekend. They seem a LOT happier today.
The Elector is so expensive I think we are going to try repeated flea baths and maybe the ivermectin also before we bite the bullet & get the pricy stuff. Fortunately I only have 6 hens so it is not too hard to bathe them all.
I'm sure it's possible that I missed areas, my coop is kinda hard to get into/maneuver around. The way it's built I'm not sure even paint would be able to get in all the hidden areas. Sigh. A plastic coop is sounding good right now. No wood for mites to hide in.