Deep liter worked for me. At one point I had about 50 birds and would bring home all of my saw dust off the table saws and shapers and planner, the big shavings and curls, a little actual dust or powder mixed in. Dump a few bags in the coop and run, chickens terrified of the change in their coop no matter how many times it has been done but after an hour standing back gawking at the mountain of shavings they get over it. You have to turn the liter under the roost though to keep the flies down.
Poop and flies is like politicians and money. Make one go away and the other goes too.
So, I read on here about using vanilla air fresheners, like the little tree ones for the car. I put 3 in my run (I have a 35' x 15' x6' run) and 1 in the coop. No flies. And I'm in west texas where it's hot as satan's balls. Coincidence? Maybe. But for now it's working. And its keeping my run and coop smelling nice instead of like satan's balls.