DISCLAIMER: I am not a gunsmith. I pretty much just copied what a real gunsmith does, and even he says not to attempt it. I took a risk doing this without proper training, experience, and tools, but I calculated the risk and decided that I could do it.
This is an Iver Johnson .32 revovler. It was handed down to the sister of a family friend and I decided that I'd like to try my hand at converting the rust on it. It really didn't have that much rust on it, but there was(and still is) pitting on the barrel, and there was some places where the finish had been stripped.
The method for converting rust is very simple. We got a steel pot from Walmart for 8 dollars, a wire coat hanger that was bent into hooks and a rod for holding them up, a drain trap to hold the small parts, and a bottle of cold bluing solution. What you do is disassemble the firearm, hang it in a pot of water, and keep the water at a rolling boil for about 40 minutes, adding water if necessary. Then, you take the parts out, card them(with fine steel wool or a carding wheel on a motor/drill), and when you've done that however many times you deem necessary, you soak it in kerosene overnight.
If you wanted to take this a step further, you could rust blue the sections where the finish has been rubbed off. That would involve a rust blue solution and a steaming chamber(which can simply consist of a clothes steamer and a cardboard box), but I decided to just use cold blue solution.
If you look at the 3rd picture, you'll see some pitting that the rust caused. Pitting is literally where rust has eaten into the metal, and it's impossible to completely revert. It's unfortunate, but unnoticable from a reasonable distance. Also, we gave the cylinder to a gunsmith, because it was missing the ejector star.
Update: the gunsmith did not have a star that fit. Because these were made pretty cheap, the parts are hand-fit. Bummer.
Speaking of stars, here's my brother's Star BM. Fun fact about this pistol; it's Spanish police surplus, and back in the 80s and 90s, movies that wanted to have M1911s and didn't want to spend a lot on them just used these, because they look pretty similar.
Again, I disassembled the gun as far as I felt I reasonably could, boiled and carded twice, then soaked in kerosene. There was no pitting on this one, but there were more spots where the finish had been removed. For some reason the barrel, on the top of the chamber(which shows through the ejection port), had all of the finish taken off of it. I'm not sure whether or not this was something that was done to make it look "cooler", but I decided to put some cold blue on it(which you can see in the last image). The rest of the barrel was blued, so I saw no reason that this area shouldn't be, and it's not like there were clean lines between the blue and the white.
Both of these came out very well, and it was very rewarding to see the final result. It's crazy to think that some "gunsmiths" will take a full on wire wheel to guns when this is what a pot of water can do!