Got a fly problem around your coop and run? Here's a solution you're going to have to try to believe. It's inexpensive and effective: vanilla scented automotive air fresheners. You heard it right: vanilla Christmas trees.
I do not claim to know WHY they repel flies, but I can attest that they do. Deploy an army of them liberally around your coop and run where they will remain relatively dry for maximum efficiency and economy. I use 9 of them at a time.
Personally, I don't just want the flies to relocate (eg: migrate up to my house or garage), I want them GONE, so I use two Trap & Toss® fly disposable traps, one near each coop. I buy the traps at Tractor Supply for about five bucks each. Be forewarned: these traps contain the fetid stench of a thousand garbage cans containing raw meat, locked in an air-tight garage during a month-long heatwave. You really don't want to spill this putresence (or stand near it, for that matter). Somehow the flies prefer to the smell of death to vanilla. Go figure.