The main reason few local gunsmiths do hot salt bluing is not the need for good polishing, but the rules laid down by OSHA and state safety and health administrators. The process is highly dangerous, and regulators require emergency showers, filtered ventilators, and other expensive safety precautions.
Some folks who claim to have done hot salt bluing say there is no danger and that they don't see a need for protective clothing or even eye protection. I strongly disagree, having seen what those hot salts can do to the human skin.
One of the oddest incidents involved an experienced gunsmith who did a lot of handgun work, mostly 1911 pistols. He blued magazines by giving them a light polish, then tossing them in the tank, fully assembled. He did that with a Browning High Power magazine, not knowing that the BHP follower is/was aluminum, which bluing salts dissolve. The follower dissolved just as the smith was leaning over the tank, and the spring threw the hot solution in his face. Fortunately, he was wearing goggles, but his face was badly burned and he suffered great pain for a long time.
Jim