"...Was wondering what you use to polish the feed ramps on an auto..."
Which begs the question: Why do your feed ramps need
polishing? If there has been no malfunction, then the real reason you want to polish them is because you just want to have the experience of doing it, or because you want it polished for the looks. If it is not broken, do not fix it. If you are going to shoot some rounds that may hang on the feed ramp, try them first. If they function reliably, the ramp does not need to be polished. Ask yourself; Is it required,
or do I just want to mess with an expensive gun and risk damaging it? If it is causing a problem, use no power tools. Obtain a wooden dowel (as a backer), that matches the radious of the feed ramp and use 120 wet or dry, then 220 wet or dry and call it good.