I have a 916 with a polished swing arm done by the previous owner. My question is, if I wanted to return it to the original finish what is it. The wheels have painted black, I quite like them what does anyone else think about the effect on resale value
Cheaper and better to buy a second hand one. You can pick up a decent one from £100 to £150 in decent condition.
They have a textured finish which I doubt could be correctly replicated. You could try a textured paint such as that used on car bumpers, how well it would match and last I don't know.