Well, nothing is going to match your paint exactly, since you've probably experienced some fading or whatever. If it's just little nicks and stuff, don't worry about that too much. Parts stores have Plastikote (sp?), and that matches closely. The only way I can see getting an exact match to the actual color of your car now is to have a paint shop or body shop mix some for you, and chances are that'll be expensive.
And since you're just repairing nicks I don't see a reason why you should need to sand down and go through the whole thing, so just wash down and brush the touch-up on there.
