Dave......I keep these handy for touching up paint.
http://www.tcpglobal.com/TCP-MB-2420...g#.WHvM14WcGZ8 I think Harbor Freight sells them or you can order them online. Depending on the scratch, I do different things. On the black areas of the coach, where it's a thin scratch, I use a Sharpie in the scratch and the buff when dry. The larger chips, I used the brushes I linked to.
Sometimes, you have to do the touch up in two or three tries. The first one is usually shallow and you still see a hole. A couple of more follow up applications fill the hole. I let it dry for a day or so and then buff.
I've been doing it for years, but have found no matter what I do, you'll never get it to disappear. I think some of these custom restoration shops actually use an airbrush to fill in chips and scratches.