I have had to put up with a lot of stubborn hoof-pickers. The trick I use, and works 97% of the time is: run your hand fully down the leg and squeeze with your thumb and index finger between the fetlock and the hoof. I rest the leg on my leg, so the horse has something to lean on, instead of balancing on three legs. I tend to lean into the horse a tad bit too, especially when I am trying to get its hoof up. It works for me all the time. Meanwhile, I have a buddy up in front praising and distracting the horse with some yummy treats. When I get done, I praise the horse many times and give it another treat myself. Remember, be careful of the frog, for it is very sensitive.

Be sure to get any and all pebbles and stones out of the hooves, its hurts them pretty bad.