Hey! Good to see you around the forums Of course, I've always got the fly spray, You can also get the tape, and there are roles that you can get that stretch across the barn. My uncle uses Fly predators in his pasture and says they work great, he's had a big change when he uses them.
For fly spray I use Repel 35X with a mixture and it lasts for two days on the pasture-kept horses. Some of my horses get flies bad in one area, while others get them bad in another. If I have a horse getting them terribly in/around the eyes I just put a mask on, a few of mine, get them bad on the legs.
I've also heard you can nail up clear plastic bags (like ziplock bags/sandwich bags) half full of water, around near the ceiling of the inside of your barn. I've heard this works to ward off flies (Not sure how, if they see their reflection in the bag or WHAT) but have always heard that it does work. I was actually in an outdoor resteraunt in Key West FL this summer and these bags were hangin everywhere out there! No flies. I have yet to figure this one out...ideas anyone?