Horse Scared Of fly spray?

Ok so My horse is on off the track race horse so he should be good with fly spray. But one day when I wasn't there a girl who works at the barn put battle on cross tries and apparently left him there for a bit and when she came back he was kicking and shaking to get the flys off. The Bombers are out! This girl decided to fly Spray him. I only Spray him in hand never on the cross ties, but this girl did and he freaked and he brok off the cross ties. So now I have a horse scared of fly spray battle see's the bottle and starts backing up and if you spray him he wants to take off i had him trotting in circles around me to get away. what are sum was y'all would use to get him to calm down and get fly sprayed. Thanks a bunch and no unkind answers.