Jim,
I don't remove the old bluing with chemical remover prior to polishing but toyed with the idea of using brick cleaner to do it. However, I decided it would save time to clean it with acetone to remove the oil before polishing as oil residue clogs the abrasive cloth. This is in addition to my post polishing acetone cleaning. I am interested others experience, especially if only "spot polishing" might be enough before bluing.
Mike