Rust Encapsulator As Primer On (Mostly) Bare Sheet Metal

[AU Doc]

I am having the body work done on my C10 project, and there are a few places were some surface rust popped up where new panels were primed and then blocked back down to bare metal (see the pictures) and then didn't get primed again (for a couple years). The FAQs on Rust Encapsulator say I can use it on just about any surface, including "mixed" surfaces that have bare metal, surface rust, and some paint/primer.

My question is, has anyone had any luck under those circumstances? I'm afraid that if I try to sand out the surface rust, I'm going to end up with very thin metal and/or change the body lines. I'm also worried about adhesion to the other primer as well as the new paint to the Rust Encapsulator.

Thanks in advance!