Luckily I haven't had to do it to my Titan yet but I've done it on past vehicles that I've owned. I can't for the life of me remember the brand name that I bought but I purchased it from a paint supply store that specialized in vehicle body shop supplies.
Get the one that looks like a touch up kit, it will have a small brush attached to the lid. For tiny scratches you can use a toothpick to fill them in so you don't get any color build-up on the good surface. Be sure to match it up perfect because it's a dye not a paint so it will change the color of anything it touches. Good luck and be sure to take some pics, that would be an interesting how-to article to have in the Tech section..