I use a 800 grit wet/dry sand paper, if there super black and green then a heavy paper then polish with the fine,, use no oil.. 400 to 800 paper you can find at most any building hardware store , thats the black type paper , also I use that to clean and polish the machine heads yep right over the decals,, but kept it WET.. Thats known as color sanding same as done on custom paint on fine cars.. thats why they shine so much ..