New cam issues,

I like using the 30% vinegar (get it at Home Depot or Lowes) to remove rust like this. Just spray down and wait an hour or so. Then just rinse off with water or spray down with brake cleaner. Anything further I'd use 800 grit to polish it up.

Just watch out for that vinegar. It'll take your breath away and leave no apologies. But it'll also open your sinuses!