Thats the best way in a perfect world..however, no matter how much attention you pay at mixing your paint, and no matter how perfect you THINK its going to match, you will be in for a rude awakening if you paint the panels off the car, then bolt them up. If your car was painted 10 years ago, as was NetVipers car (and mine as well) in Japan, a totally different climate, trust me, the paint you mix has a 1 in 10 chance of matching exactly, therefore, you must bolt up the panels (after trimming which takes no time), and paint them as well as blend into the panel next to it, so even if the paint is a shade or 2 off, it will gradually fade into the next panel, and the naked eye will not be as apt to notice the shade difference.