My coop is covered in flies all the time. I bought a 10 pack of fly tape and put one strip in the run and one outside. The one inside was covered in an hour and the one outside only caught small bugs and a moth. Unfortunately, the strip in the run somehow disappeared. I don't know if they ripped it down and buried it or what happened. Anyway, it took control of the fly issue while it was hanging. We live in an old farm house and that coupled with the daughter running in and out all day long we fight flies all summer too. Fly strips are your friend, but they aren't really attractive hanging around the house.
Chris