We use a carbon steel wire wheel on a grinder for most of the bottom side,and to get any compound curves,and edges. After that we hit the rest with a D/A sander, and 80 grit. If you run the sander nice and flat you can find most of your low spots,and dingers. I make a note of where the big low spots are before I dig and strip it completely. Some old paint can get gummy if it gets to hot so move the wheel around to a fresh area if that starts to happen, and go back to it after it cools a bit.
