Ditto on Dickson suggestion to use Epoxy Primer. Anything else will allow moisture to penetrate to the metal.
You WILL have to spray the primer (I just did mine last night and it's not that tough, just allot of prep work and pre-cleaning, but you can do it in a garage/shop if no paint booth is available to you.
I suggest you use PPG's DPLF series epoxy primer. It comes in various colors. Grey is fine for the sealer coat, then you'll probably want to use a yellow primer/surfacer to do your blocking and final sanding with.
BTW, here is a link to a great forum to ask body/paint type questions. http://www.autobodystore.com/cgi-bin/config.pl?index