I used 3M™ Microfinishing Film on camshafts and cranks. I got it from my local machinist, it came in rolls. I'm not sure what grit it is, it's pretty damn fine though..
I use 1500 grit sandpaper lubed with motor oil. VERY smooth, polished surface while removing minimal material. Cut long, thin strips (lobe/journal width), wrap the around the lobe/journal, and pull back and forth so you exert even pressure across the lobe/journal face.