YES!
We never had fly issues until someone bought the farm across the road and brought in horses. Oh my, the flies! We use horse pellets so there's no fresh poop for them, beats me why they came. I called my sister, who raises turkeys commercially what do they do for flies? She told me about the PT Alpine. I bought a can. It's pricey, but that was five years ago, and I still have half the can left.
All I do is spray a dot on the coop's walls out of chickens' reach. Like one dot on the wall on either side of the window where the flies were the worst, that was enough. Of course, my chickens eat the dead flies. They are little silkies and are fine. I read somewhere else they were safe to eat, too, just in case.
These dots I spray last about a month. A little goes a long way, so you don't have to overdo it.