It has been said, "Any fool can blue a gun!
You said "The prep and polishing seems to be key."
Polishing IS the key!! Prep is perhaps a meaningless word---and if it isn't meaningless, then it's ambiguous.
Let's think of prep as keeping everything squeaky CLEAN!! Bluing is a process of "controlled corrosion". Another name for bluing is black oxide. That which is controlled is primarily time and temperature---the amount of time exposed to corrosive agents (bluing salts) and the temperature to be maintained. This being applicable to "hot tank" bluing----as practiced by damn near any and all (and any other process with heat involved)---and requires special equipment. Processes requiring little more than patience and elbow grease come under the heading of "rust bluing"------a favorite of the do-it-yourselfers.
Polishing is the name of the game! Perfection is required. S&W uses/used (??) formed hard leather polishing wheels---formed to match the many and varied surfaces of the gun-----and they use/used them to perfection---absolute perfection. You can achieve the same level of perfection polishing by hand. It ain't easy! It takes A LOT of time. There are NO substitutes!
Your alternative is to find (FIND!!) and pay someone to do it for you. Finding that someone is a terrifying responsibility, because like I said, "Any fool can blue a gun!" I've had exactly two guns refinished. There was NOTHING terrifying about it because the factory did both of them. That was then, and now is a whole different ballgame!!
S&W used to believe they would be successful if they built the best possible product for the price. They did that, and it worked---for the first hundred years. Then they got the idea they could be as or more successful if they built the product at the lowest possible cost. Now, coming up on seventy some odd years after the first hundred, they're still trying to make that work----yet another terrifying thing.
Ralph Tremaine
A thought---about a short-cut---that works---if you find you're happy with the finished product----"bead blasting" instead of polishing. Bead blasting is a surface treatment accomplished by subjecting the surface to be blued---or plated to media delivered by high pressure compressed air. You end up with a matte finish instead of a high gloss finish. "Glass beads are likely the favorite media, but there are others---including sand---and crushed walnut shells, of all things. The proper, consistent delivery is accomplished by control/selection of the media, the line pressure, the distance from the work piece and the angle of attack. Do it, or have it done by someone who knows what they're doing (and does it)! I have used glass bead peening to clean engine parts from my race cars. That's pretty much of a no brainier because your goal is simply the absence of crud. What you learn along the way is you can control the appearance of the finished product by controlling the variables noted above. It's A BUNCH faster than polishing-----but the finished product is entirely different---but can be quite pleasing. I had a Colt Government Model transformed into the "Master Grade" conversion by Wilson Combat. It was a "Pinto" finish---blued slide/plated frame, both prepared by bead blasting---by EXPERTS. It was a gorgeous gun!
