Submitted by Dan (aka snomuncher)
I've had to repair a few paint chips on my silver car. Most metallic paints are difficult to match, with silver being one of the toughest. The metallic elements in the paint don't seem to lay down in the chip and provide the same reflectivity as the surrounding area. After a bit of experimentation using a variety of techniques, I found several tricks that helped quite a bit for the metallic silver.
One is to fair the edges of the chip into the surrounding area. Sharp edges are near impossible to color blend otherwise. This will enlarge the chip area but will produce a more uniform reflective repair as discussed below. I use a fiberglass nick sander to do this.
Another is to mix the base paint and clear coat together. This is an advantage because it allows the paint to lay into the chip level with the surrounding area, not requiring additional build up of the clear coat that will need to be sanded or buffed level with the surrounding area.
The third is to mix the paint to a viscosity that allows it to flow freely into the chipped area. Many touch-ups are lacquer-based and adding a drop or less of lacquer thinner onto a dab of paint-plus-clear mixture will thin the mixture enough to flow rather than have to be brushed on. This is where fairing in the sharp edges becomes an advantage; it allows capillary action to let the paint flow freely as if filling a small “pool.”
The last is to experiment with tools other than a brush for repairing chips. One size does not fit all repairs. The brush in the cap that is included with most touch-up paints is too large and holds too much paint for most minor chips, and will leave a "glob" on the surface that does not match well with the surrounding area. I have successfully used both flat and round toothpicks to flow paint into chips- and don’t use too much paint.
Patience is a virtue here and it may take several tries...removing the touch-up with lacquer thinner will allow you to start again if you’re not satisfied. Good luck.