I had one of those bag/fly trap thingys, and hated it! It smelled like a dead body, and yes, it caught a lot of flies, but I think it actually attracted more than the coop did. It also was attracting much larger, meaner looking ones! So I had to dump that nasty thing.
At night, when the chickens go in the coop, I sprinkle DE, till everything under, and add a fresh batch of leaves on top. Sometimes I would do this process in the middle of the day. I also scoop any obvious, easy to see poo from the coop and run. I only have 6 birds, so it's really not a big deal to do.
There's a whole thread on here about using those Vanilla air freshener trees that you hang in your car. They are inexpensive, and I figured it would smell a lot better than dead body smell, so I hung a couple of those out there, too. Here's the thread:
https://www.backyardchickens.com/forum/viewtopic.php?id=368487
I've also been sprinkling the dog poo with DE.
Another tip I've heard, but never tried is a Ziploc bag about 1/3 filled with water, and a few pennies in the bottom. I don't know why they don't like it, but it's supposed to repel them. Again, I haven't tried this one, so I don't know, but I suppose it's worth trying.
Good luck!