When I first got my 9 year old mare, she wouldn't let me pick up her back feet. She would, after a lot of leaning into her sholder and pulling, let me pick up her front feet. I kept at it, and after a week I could pick all her hooves without wrestling. Let your horse get to trust you. When you reward it, do so at the feet, so they associate you being down there with good things. This really helped me. I don't just drop her hooves either... Make sure to set it down gentle so they don't feel like they have to be on guard for the drop. You'll get it! :) A lot of these tips I read about in different threads on here. Good luck!!