You advised a Machine Shop was close by, see if they have any Roll Emery Paper. Most Roll Emery paper is one inch wide, but new purchases comes in fifty yard rolls. It comes in 220 and 320 grit, good grits for what you want to do. An old engine repairs person years ago showed me how to use the roll type emery paper to polish a crank. He took a one inch wide strip, three foot long. He split the strip with scissors to have two one half inch strips. He then made one complete loop around the crankshaft with one of the one half inch strips. He pulled on each end in a back and forth motion. Polish pressure on the crank was constant all the way around the crank. He polished a mirror surface on the crank in a few minutes.