I make sure they are completely brushed out. I take a cotton glove and some what soak the palm(with my hand in it)with good fly spray and wipe their entire body thoroughly. I also pack a can of Deet(If ya' need it, you need it.)
LOVE the glove idea. Grace (my mare) does not like the spray bottle, so I use an old rag to wipe her down and put on her fly mask every morning, and I wipe her every evening. I always wipe her between her hind legs, all up in there. I wiped her before the rides as well, naturally.
It's up under her belly that the biting flies drive her CRAZY... up under, on her soft teats. Even in the field, she's very sensitive to flies, which is why I am diligent about using the wipe daily AM and PM. On the trail, the sweat obviously attracts them... and seemingly, mostly "down under" her. I really didn't notice any flies on her butt, where I could get them.
So here's my big question: "Is getting off to deal with flies a good idea?" She's going nuts under me, and I'm in the middle of a trail. What to do? I don't getting off to shoo flies is wise, because 1) they come right back and 2) over time, won't she get into all kinds of mischief when she realizes that behaviors can get me off?
On the other hand, to force her into working when she's really being bitten in some tender places seems cruel and unusual. So, "fly fixes" (sheets, wipes, etc.) aside, if flies get through whatever precautions I take, how do I best deal with her bahaviors, do you you think?