If your truck is like mine, a lot of it will sand down to bare metal & get the rust off with a DA. Some of mine I have had to use my electric angle grinder with either the 3M stripper or 60 grit flap disc. Anything beyond that you could sandblast or use Ospho (I think it is spelled that way). A lot of the smaller parts I used electrolysis and got stuff pretty clean. Once you get the metal clean I would get it primed & painted as soon as possible.Epoxy primer will hold it best for a while, but a cheap primer will not keep it from starting to rust again. I had all my paint(urethane) mixed at one time and am painting each panel as I go. As long as the paint was all from the same batch it should look O.K. painting panel by panel.I also am using POR-15 on the inner fender aprons & the backside of all my sheetmetal parts. That should hold the rust off for as long as I own it.

1957 Chevrolet 1/2-ton Stepside LB in the Gallery
My Photobucket shots

The person who has nothing for which he is willing to fight, nothing which is more important than his own personal safety, is a miserable creature and has no chance of being free unless made and kept so by the exertions of better men than himself." - John Stuart Mill (1806 - 1873)