I had both my frame and cab sandblasted. But it looks like I had way more rust than you do. Even sandblasting doesn't reach all the nooks and crannies, but it's better than manual methods. It's also WAY easier. The only effort is opening your wallet.
I built a rotisserie from two engine stands for working on my cab, and then adapted it for doing the painting on the frame. See the pics attached.
I have no opinion on POR15, never having used it.
