Pat66 posted good advice.

I will have someone else paint my 54 pickup, which already has all metal prepped and has been epoxy primered (to prevent rusting).
Some "filling/surfacing" will be needed.

My order of metal parts painting will then be (primer/filler/surfacer and urethane final coat) :

metal bed parts (see note below)

cab exterior (gas filler tube)
cab interior
seat frames

inner fenders
outer fenders

doors
hood
front/rear valances

chromed grill "details"
running boards

Oh yeah, bed boards will be painted, after bed metal parts are painted (so the bed can be assembled early onto the frame).