I hate body work........it is my least favorite part of a build. A lot depends on the body you start with, be it fiberglass or steel. Obviously, the better the body the less work you will have to do to get it straight enough to be shiny.
My Speedway body took a whole lot less work to get it straight enough for black than my Son's Total Performance body took to get it straight enough for blue. To be honest, I am very disappointed in the quality of the TP body, it is too thin, and now he is getting shadowing through where the wood was bonded to the body. The car will need resanded and repainted somewhere down the road, and it has only been painted 8 months. Mine has no shadowing whatsoever, and I attribute that to the fact it is a heavier layup. I'm sure TP will say it is because of the way the wood was installed, but that would not be true because I have two Speedway bodies, a '23 and a '27, I wooded both of them, and neither one had that problem.
Color also enters into how much work you will need to do, some colors require a very straight body and some colors will minimize waviness to some degree.
Don