I do this a lot on frames, cabs, fenders, all of it. Maybe its just me, but I find it impossible to really feel what is straight, and what is not if I use mechanical or pneumatic sanding equipment. In fact, I have spent just as much money in long board hand sanders as anyone who buys DA's and the like. I have 36" long boards, down to the small ones. I use PSA stick on paper in only 3 grits until its time for wet sanding the clearcoat at the end. I use 80, 220 and 400 then I rely on the PPG primers and paints (Rage Gold filler and Polyester plastic) for the finish. Without long boarding all body parts, there is no way to ensure you have straight panels.
To get the old girl to bare metal, media blasting is my choice and I have learned to do that myself if I want it done right. #1 Silica sand removes all the paint/rust and there is NO scratches involved to discuss in the first place. IF I were to use a DA to get the truck down to bare metal, it would be 80 grit or higher. Paint and primer has a tendency to shrink over time and using anything more coarse than 80 is asking for trouble. Truth is, this whole discussion is not for just anyone. There is a lot of finesse to this kind of work and takes years to perfect. Once you have done about 5 to 10 entire trucks, you can call yourself worthy of even doing it in the first place. Its just like anything else, practice makes perfect. I am in my 35th year of practice (on these trucks)with no end in sight!
