Until it gets stretched, torn, or beaten to a bloody pulp, body metal has a "memory". It really wants to go back to the shape it was stamped out to be at the factory, so a good body man just helps that happen. That usually means you need to work slowly and carefully, and resist the urge to pound away with a BFH. Fortunately, the mild steel these old trucks were made of can handle quite a bit of massaging to get it back into shape, and a good metalsmith will only need to use very little body filler, if any at all, to finish things out. Newer, thinner body metal with more modern alloys doesn't work so well when trying to bump dents out.
Jerry
