AFAIK, there are only two cost-effective ways to refinish one - have it plated (black chrome, pewter, silver, etc), black Tefloned, or "colored" via a gun coating like DuraKote or faux case colors.
IIRC, there IS one shop doing a coloring that looks like bluing, which involves a few pre-treating/plating processes - but I disremember more details, at this remove.
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