Louie has never really loved being fly sprayed, but having cross ties and a relatively small area to work in, I can usually get him confined and still enough to spray it on him through his dancing and discontent. Well today I decided it was time to tackle the spray bottle issue. So I filled up a fly spray bottle with water and we headed out to the arena. I started spraying on his front left leg and he walked a circle around me, then eventually stopped, stood, and tolerated the spraying. I made a "rule of 10's," and decided that I would stop spraying him after 10 sprays of him standing calmly. So I sprayed and sprayed until he stood calmly, then continued for 10 more sprays, stopped and petted him. Repeat.
Once he accepted being sprayed without a fuss, I moved on to the other front leg and repeated the process. Then I moved up to the elbow, shoulder, neck and belly. By the time I got to his back he was pretty bored with the routine and I had already filled up my spray bottle twice (my forearms are going to be aching tomorrow and Wednesday from all that excessive use of my fingers!). When I got to the hindquarters and hind legs, I got a more heightened response, as I expected. So this took a while to get some relaxation, but eventually we got there.
After using 3 full bottles of water on him and thoroughly soaking my poor horse, we called it good for the day and went to get a little fresh chow. I attempted fly spraying him while grazing (with actual fly spray) and it was a bit of a different game outside. Luckily he only moved a little bit, so I was able to get him fly sprayed pretty well without wasting too much.
This will be a multi-day lesson for Louie, but hopefully he will stand still to be sprayed by the time we're finished.