My question is my 80 Malibu Had tiny rust spots at the bottom of both quarters. Very small I ground it down to bare metal. Put a little fibeglass over it primed and painted entire car. As I was sanding to prepare to buff I noticed tiny little bubbles so I sanded it flat and waited a couple of weeks and they are coming back. Is there a better way of fixing these spots maybe some kind of weld then grinding it down. This is the only rust on the entire car. An like I said it is very small. I did not even know it was there until I was getting car ready to paint. Paint came out very nice but I would like to fix this before I buff quarters .