I had a similar problem with my front bumper got destroyed in stone chippings i got 100mls of touch up paint from halfords and rubbed it on with with a cloth you can see a few streaks etc but only when you really look and it takes the eye of the white chips until i can get the money together to sort it properly ive some damage at the side of it as well where i hit a kerb and its hiding that quite well too but as i say its only a temporary solution till i can raise the cash to get the front bumper fixed and resprayed but just to look at it it looks good