I've been working on some Jeep wheels that were badly pitted. They came back nicely with wet/dry sandpaper starting with 220 grit, 400 grit, 600 grit, 800 grit. I think I would go to 1500 on the crank arms to get a nice polish to them. My wheels look good from 10 ft away, they'd look better if I'd gone to a higher grit. Use wet/dry sandpaper and rinse often.