Check out Touch Up Paint from PaintScratch.com. I had great results with their spray. Did a full size Sunline lip and am really happy with it. It's a 3-step white, pearl, clearcoat process that you can't tell from the original from 10 feet. The Pearl stage is not metallic, but you can't see that unless you're right on top of it. Guys why don't you post some pics of your damage so we can judge what application method would be best?

I've used Dr. Colorchip as well. If they scratch isn't too big, it fills in very nicely. Just make sure you follow the directions and shake the buffer solution before you put it on the rag. If not you're going to get the nice little haze...

If they are deep I would look at trying the Applied Colors kit. It comes with 3M Putty to fill in the scratch before applying the paint. Same concept can be used with the Dr. Colorchip kit you would just need to pick up the 3M Putty separate. To me if its to big of a scratch the only fix is going to be to get a body shop to repaint the piece that is effected.

Fix Deep Car Scratches: World's First DIY Kit

Well if you know the answer to this question it will answer your question. What is wrong with Nissan paint in general?