The bike is secured in a Frame Jig and them pressure applied to bend everything into alignment. No heat was applied to any of the bikes I've had straightened and the frames came back with out marks.
Hmmmm... It was over 10 years ago when I checked this out at a Computrak near Dallas. It was closed years ago. Only open a couple years. Anyway, they told me about the heating and specifically said they do not repaint the frame, that it was my responsibility. Wonder what was changed? Maybe they came up with a better system. Do they still use lasers for measurement?