I've worked on a few newer cavaliers. Let me tell you there isn't much to the metal on these. Take a finger and push and you can literally see the metal move in. I didn't have any real problems with regular or finishing filler getting it straight, but it takes a gental hand. Welding on that sheetmetal is fun. I did some filling of the holes from the factory spoiler. All was going well until the very last one to fill. Warped the trunk, and I had to pry and pound to get straight again as well as get rid of some oil can after the fiascal. Talk about po'd. Quite a difference from the 60's cars that have around 18 gauge sheetmetal to work with. If it pops in with a little pressure and stays in or pops in and out, you obviously have some stretching to take care of like Brian and the others said.
How about the high build primers? should they not take care of any pinholes or small scratches and be fairly easy to sand out..??
Yes, but pinholes sometimes I found you need to take your finger and smear the primer while wet into them. Put on enough coats and it should sand out, or catch this in the first round of primer, and sand and apply more primer.