Don't get down just because you're on the small side; I'm 5'5 and have done my own horses for nearly 10 years now...yes, it can be hard on your body, which is where good training comes into play.
I use part of Clinton's methods, and another method that is sort of my own idea (although I'm seeing it out there now, by other trainers), in which I teach them to give to a feel by putting a cotton lead around their foot, and gently put pressure on it till they shift or lift the foot, then release; It keeps me safely out of the way if he decides to jump or otherwise refuse to give to the pressure, as I can stand at his shoulder, and just move with him; my head and the rest of my body is out of the way. When he has that down, then I move on to using my hand to ask him to give his foot. My mare is learning to pick up her feet by a simple touch\light tap to her knee; she's got her front feet down, so now I am working on the rears. The yearlings I am training are also learning to give to the touch, but they have a way's to go yet. But they pick up their feet nicely, and wait patiently for me or studentst to get done picking them out, and they are pretty easy to trim.
"The ideal horseman has the courage of a lion, the patience of a saint, and the hands of a woman..."