under vinyl top treatment

Hey gang! What is best to paint under a vinal top? I am replacing the top on my wife's 73 swinger. I took the old one off, and cleaned all the glue off. Now there are some bare spots. was thinking por-15 the entire roof after hitting it with a DA/320 paper? the car had some rust on the windshield frames that I took care of and don't want coming back, so I thought por-15 would work good? Im open to suggestions! Thanks guys!