Dealing with a horse that won't lift its hind leg for shoeing

Last week, I had a gelding that refused to lift his hind leg for a trim. He kept shifting his weight and leaning away every time I tried. I used calm voice commands and even brought out some treats, but nothing worked. My buddy had to hold him steady while I gently tapped the leg to get it up. It took forever and left me pretty frustrated. How do you handle horses that just won't cooperate during shoeing? I'd appreciate any advice or stories from others.