When I bought my gelding, this was the only vice I was *told about, lol. He was terrified of the flay spray. So I Tried to spray him to see the reaction I would get. He started dancing around with his nose in the air. He is pretty respectfu and wont run me over or yank the rope ou of my hands so this is the appraoch I used on him. I took an empty fly spray bottle, and filled it with water. I sprayed some real fly spray on a brush anf brushed it into his neck and forelock so he hat the smell. The I start spraying him in a rhythmic manner spray, one two three, spray, one two three... I kept this up as he was dancing around me and stopped spraying *the moment* his feet were still. Then I let him relax and gave a treat. Did this agian, he stopped in 30 seconds, then the next time in 15 seconds. By the 5 or 6 time he was just bringing his head up. Then I would stop when his ears would relax and there was no white to his eye, showing him that what I wanted was him to relax, and thing end quicker. I alway offer a treat to to associate positive things. I NEVER spay at the face, I know alot of people do, but imagine getting that in your eyes, nose and mouth-would you stand still? I spray on a small sorft brish for the head face area, and wipe on. I also use a brush on the body while the spray is damp to work it into the hair for a longer lating effect (but the stuff I use also has coat conditioner and sunscreen--my pathetic attempt to keep my black horse black), but I sure lovw the smell XD
I did this exact same procedure with my mae when I got her, who was never sprayed, but because she is a dominant and pushy type horse, I lunged her first to establish dominance and MY space. It took a few minutes longer, but each were desensitized within a day and now stand untied in the field for a spray when I approach them.
Sorry about the novel