Rick, to prime between two joining surfaces, just clean then prime.
If you are going to paint, then scotchbrite with 50/50 mix, then clean with straight metho, then final wipe over with the prepsol and then etch prime, then apply primer and then colour over the top. If you are going to do this it is best to paint wet on wet, it's more intense but it is a lot quicker and a lot less work.
Jeff