For small rock chips on the front, and until the off-season arrives when it can be fixed properly, I do this:
First you need the correct touch-up paint. You can get a small amout from an auto paint supply store with the paint code.
TEST that sample on a scrap piece and hold against vehicle after it dries.
If paint is close enough, use a small amount in a receptical and then THIN with automotive paint thinner, found at the same auto paint supplt store.
With an artist brush, dab a small amount ( and I do mean small ! ) into the chip. If it's thinned enough it should flow into the chip hole and no farther, but be prepared to catch any over-flow.
Let dry completly. Repeat above process, layering paint by very thin coats until chip hole is fairly full.
It's important not to try and hurry this process, best results are achieved by being paient.
In the winter, after the cruising season is over, I have those chips fixed by my painter. ( He loves me ! ) I buy the touch-up paint by the pint. This will usually last two years and is used by my painter so the pint goes a long way.
One pint was used over two years to touch up as described above AND by my painter to repaint three fenders..
Val