For resto, you will still need to remove paint to get right into everything. There are several methods, media blast... Do NOT sand blast panels..and the best of all is chemical dip.
I used to Sand disk till just see steel in the scratches, then ether media blast or chemical dip.. Removing mostly of the paint by sanding disk meant when media blast and chemical dip , what is left comes of very easy.. which cuts back costs quite dramatically.
Still shop around some media blast / dip shops will still charge full amount regardless.
Also when strip back steel, get it it seals almost immediately.. epoxy it the usual these days
Most restos , once stripped up will then see far more corrosion than excepted, espec in seams, and will pick up old poor workmanship , from straight bog to fiberglass patching...to foil tape.