I haven’t tried this, but I hear people see them all over beach restuarants.
take a ziploc baggie that actually zips closed and fill with probably 1 1/2″ of water. Plop in numerous pennies. Staple onto places around the coral/barn or what have you.
I read up on it and it states that the flys get dizied or irritated by the light bouncing off the pennies and the illusion water created.
Like I said not sure if it really works.
We use a topical fly repellent. Have you heard of Frontline or K-9 advantics? It’s like that but for horses. We get it at the local Farm & Fleet. It is called Equi-Spot. We find it helps, but it doesn’t solve the problem.
We use Pyranha Fly Spray, think it works the best. Endure is okay too.
Also, we sheet body, head, and legs.
We use Swat topical ointment for belly buttons because the flys love it there. The Swat is wonderful. used I think to protect wounds from flys so it is really repellent.
OH! there are also these little bugs that you can buy that eat the larva of the fly. We used them twice and found it helped. Though I can’t for the life of me remember the company that sold them. I saw the commercial on RFDtv.
Maybe you can try the fly zappers?