Hi im lexi! You should first get a clear spray bottle; like the fly spray ones; and put water in the clear spray bottle with nothing else just water. And you should hold the horse when you do it in case he freaks out. Anyways spray the water in the air and see it he is ok with it. Then if he is then spray it towards he body and get closer and closer and when you get to a spot where he doesn't let you get any closer show the bottle to him and try to make him smell it then rub the bottle on his body where he was scared of it. It is a long process and it probably will take him a while to get used to it but keep doing it over and over. And once he isn't scared of the bottle with water in it switch back to the fly spray bottle. And it he is scared of it go back to the water bottle until he shows no fear. I hope this helps!!

Lexi