Does cold blueing work if applied to metal that still has a rust-colored tinge? I have spot-blued other guns before, but if the surface wasn't "silver" sometimes the rust would start back again. Successful results seemed to depend on completely removing any trace of rust.
It won't hurt to try. I'll degrease and cold-blue tomorrow.
One thing I had considered was de-blueing and going for the aged look, but I don't know whether vinegar will remove rust.