PPG makes just about anything you need for painting a car. IMO you cant go wrong with PPG.
SPECTRACRONŽ 315 High Build Primer Surfacer from PPG is the one favored by the guy I have doing my body work. Granted I havent painted the truck yet, but the repair he did looks fantastic.
I know this one is not specifically for automobiles but it does work great for that. But there are others specifically for auto paint. This one is for industrial uses and is just one that he works well with. Havent had any problems with automotive applications to date.
here is a before and after of the repair using the above primer
before....
after....
