Texian
If your frame is matte finished (bead blasted), you may have to have it touched up with a blast.
I haven't tried it, but someone posted that on a matte finish, you can take sand paper and lay it face down on the metal, then tap very lightly with a small hammer. Obviously, you'd have to experiment with different grits and pressure but that might be an alternative to try.
If your slide and frame are more of a "brushed" look, I've touched them up with fine sandpaper that matches the grain - again you have to experiment with various grades and pressure. The key to matching well is to move the paper exactly the same direction as the existing grain.
HTH
JSP