Here's the after photo. To get rid of the flash rust, I coated the backing plate with Rust Cure (www.rust-cure.com) using a cheap nylon bristle brush and thoroughly wiped the Rust Cure off immediately. Another application and wiping off may be needed. If you don't wipe it off, there is a residue that can be removed with re-application of Rust Cure and wiping.

Rust Cure is a phosphoric acid-based rust remover, similar to other phosphoric based solutions but stronger. For most rust removal, I am using EvapoRust or vinegar, but Rust Cure is very good to fix flash rusting until you can finish restoring the part.

My backing plates were all originally phosphated, so that's the way they will be restored. When it comes time to phosphate, I will wash off the Rust Cure, do a final pickle in vinegar, and immerse in the phosphating solution.

For parts that need to be painted, apply paint on top of the Rust Cure - do not remove it. Allow one week Rust Cure drying time before painting.

For parts that were originally bare metal, the medium gray appearance left by Rust Cure may be too dark. You can remove the Rust Cure with a hot wash, then hand wire brush for a few minutes to get more metal shine. Then immediately coat with wax, RPM, or similar. To get the right balance of gray vs. shine, you can experiment. Generally bare parts of flat, thin metal were cut from cold rolled steel that was shiny, while thick parts were cut from hot rolled/pickled & oiled steel that was gray and less shiny. The Rust-Cure gray should be about the right color for rear spring brackets and the spring plates with shock absorber mounts.

For bare metal parts that were forged or heat treated, such as suspension parts, there have been several posts here about using gun bluing followed by RPM. You can remove the Rust Cure by washing, then hand wire brush, then apply bluing and RPM. I haven't done this yet - it may work to put the bluing on top of the Rust Cure.