the cheapest method i've found was a halfords touch up kit, a pot of cocktail sticks, t-cut, turtle wax colour match polish and a final wax.
paint in the stone chips, either cocktail stick or v fine paint brush, leave it for an hour or so, then lightly t cut to flatten off blobs, polish, wax, and then it doesn't look too bad.
i know there are kits on the market, but, the reality is, however much i spend, i still apply them with the skill of a pissed gorilla...