Well, FWIW, my local body shop told me to buy the BMW touch-up paint/clearcoat and stop by and he'd show me a trick on how to do it right.
But my chip is down to the metal.
I think the rule is, if you can catch the chip in your fingernail it can't be buffed out.
E90 325i Monaco Blue, Black Leatherette, Sport, Cold Weather, Xenon, Sat Prep, 18" BBS RGR
Mods: Polorized Film for Business CD, added lumbar, rock chip on hood