I made a short video, showing how I like to cure head-shyness and ear-shyness. Maybe it will help.
The gelding in the video is a 20 year-old Quarter Horse that was left alone in a pasture for over a year. He is a chronic cribber and a cribbing collar is required to keep him from wearing off his top teeth and keeping weight on him. Having been so long with the cribbing collar in place, without having been removed except on the rare occasion that his owner rode him, it made his head sore at the poll. When I encountered him, you could hardly catch him and it was very difficult to halter or bridle him, because he would not allow anyone to get a hand anywhere near his ears, most particularly his right ear.
I worked with him for 15-20 minutes during about 3 sessions on different days, before he would allow me to lay a hand on his ears. Within a couple weeks of working with him 2-3 times per week, he was his old self again. You can see in the video that he has absolutely no head-shyness at all now.
Just FYI, the horse in the background is mine. They are pasture buddies now. The gelding still wears the cribbing collar, but I remove it several times a week, while I groom and ride him.