I don't think there's any doubt that an exceptional bluing job is 90% polishing and prep. (And I think this is why, in an era of relatively high labor costs, exceptional bluing jobs are rare on factory guns.) As long as you are actually "bluing" the gun -- controlled corrosion of the skin of the metal, to put it simply -- the key to a deep glossy finish is a really, really smooth finish when the process starts.

I am really amazed it is proving so difficult to find out how S&W blued their earlier guns...