A lead-out treated cloth used for cleaning the lead fouling out of firearms works wonderfully on stainless. My one time satin finished S.S. Colt .357 Python looks like a mirror now after a few years of casual wipe downs with it, and it was totally unintentional.

The finish on the mufflers is light years ahead of where the Python started out, it shouldn't take a whole lot of effort to make a difference.