I am painting the lower portion of my front and rear bumpers ( 84 Z28 ) with a satin bumper paint. Two small spots bubbled up a bit. Those spots were damaged a little so sanded through the outer coat. Is there a sealer that should be used in this case before paint. It is possible I didn't prep it as well as I should but will have to wait for it to dry to check.

 

Yes there is a special sealer and prep you need to use. Your local paint store will know the numbers. I use to know them i used them from a company called SEM. Alot of times they say u dont need to seal but its best 2.