While trying to enjoy a sarnie at the burger van up the road from me recently, I was being driven mad by the noise coming from the neighbouring tyre-&-exhaust place.
I commented to Tracey (who runs the burger business) that I'd never heard that much noise, going on for so long, coming from the place before. She said, "Oh, they'll be refurbishing a set of alloys again". So I took a look and it's done (at least there) by nothing more complicated than a guy using a grinding tool to go over and over the surface until it's polished back to new.