[Nickj]

I've got a 'new' case to go on my S2R.
Prep was strip all the paint, I used chemical stripper but mild shot blasting might do better but needs good cleaning after. Soda blasting would probably do nicely as it only needs a water wash off.

Then a standard acid etch primer followed by a session in the oven to dry it all nicely.

I've usually used RS paints, they have a good match for frame and engine casings and will make you up a custom match if you have non-standard colours.
Then another bake, very fine wet and dry followed by a top dust of paint and rebake.

Then a satin lacquer, looks fine and matches the other casing.

Past experience says it lasts well as a finish as with all paint the prep is what makes or breaks it.