Fly sheet, fly mask, fly boots... But your horse sweats in those, so I really don't know what to tell you. Some people swear that mixing a TBSP of garlic in their horses grain ration will help with the flies, but I've never tried it. My horse gets eaten alive by flies too...My trainer loves the DuMor brand of fly spray. It's by Tractor Supply, so it must be good lol. I personally LOVE the UltraShield Green fly spray. You can spray it on the horse, you and your dog. It's a little pricey, but it works great. And if you don't want to put the fly sheet on him to keep his coat from fading, you could add that Black As Knight stuff to his feed. It'll help keep his coat black.