This may be here nor there, but back in the academy, a fellow cadet used one of those yellow rags used for getting rid of lead. I don’t know what the chemicals were, but they really did a good job.

He used the rag to polish the exterior of his stainless S&W to almost a mirror finish. We all had a good laugh. I’m wondering if those lead dissolving rags will do at least a little work for you.