My understanding of Cerakote is that the only basic prep is a clean, grease-free surface. "Roughing" it will result in a rough-looking finish after coating. The only other prep would be the usual polishing, etc., of any flaws that you don't want to show through. Check with a reputable Cerakote dealer before doing anything!
EDIT: Area 15 is a highly recommended Cerakote dealer here in Metro Phoenix. If you don't have someone local to you, they are worthy of consideration. I'm not affiliated with them, I only know of their reputation among gun people out here.
AREA-15