Does anyone have a good technique for doing this? I tighten the calipers to the point where they rub the rotor then bend the disk away from the rubbing caliper with a small crescent wrench. While this works to a certain point, I can never get it really true. There must be a better way of doing it.

there's no better way to true rotors. if the rotor is bended 1~2 spots, you can easily true it, but if it is like wave shape, you need a rotor truing gauge to true perfectly.

I take the rotor off the wheel and place it on a hard flat surface. In my case a formica bench top. I then mark the rotor where it needs to be bent and put it (wraped in cloth) in a vice and gently tug on it with my hands. I do this until the rotor lies flat.

Note that you should bend rotors at the "arms", not at the circumference. That does nothing.