1. Wear rubber gloves.
2. Degrease the area to be blued. (Birchwood Casey Cleaner/Degreaser.)
3. Use blow dryer to heat specific area. (Heat gun would even be better.)
4. Apply Brownell's Oxpho Blue with cotton swab or q tip.
"I wouldn't recommend using Q-Tips or cotton swabs bought from the drug store. They put a coating on them to keep them sterile. I would get a pack from Brownell's that are pure and clean cotton. I have had cold blue streak and blotch from Q-Tips. Acetone is a real good degreaser before bluing. I put the part or barrel in my oven and heat it to about 150 degrees, rub it down with acetone, and apply cold blue. It takes the bluing faster and comes out darker and richer looking. After I think its blued enough, I wash it with soap and real hot water. The water should run right off or bead up a bit. That's when you know its blued enough."
5. Allow to penetrate for a minute, keeping area wet with bluing compound.
6. Either a) rinse with warm water or b) soak rag with warm water and rub metal.
7. Buff with degreased 0000 steel wool.
8. Repeat two or three times.
9. Buff with degreased steel wool very lightly.
10. Apply non-penetrating gun oil (Hoppes gun oil is recommended by the tech from Brownells).
(Dfariswheel responded to the above procedure with the following):
"I like the Scotchbrite synthetic pads, but for cold bluing I think 0000 steel wool does better. 00 steel wool or the equivalent in synthetic is WAY too coarse.
Automotive stores sell Scotchbrite pads that are even finer then 0000 steel wool, but the steel wool seems to work better. You buff VERY LIGHTLY between steps 7 and 8, but you buff a little harder between steps 6 and 7, and you use a dry pad. In order to prevent contaminating the clean surface you're bluing, you need to clean the oil off the steel wool.
I put alcohol in a cup, tear off small pieces of the steel wool, and soak the steel wool in it to remove the oil that pads are soaked in to prevent rust. After allowing to dry, the pads are degreased and ready to be used for bluing. Don't soak more than you'll need immediately, since the degreased wool can rust in hours."
Someone on Glocktalk responded: "The 3M pads usually have carbide compounds in them, much too aggressive, use fine steel wool that has been degreased. BTW, if you aren't getting good results, applying the cold blue with (degreased) fine steel wool can make a big difference on some steels.
(miscellaneous information)
(This was before I learned about point number 8) Apply Breakfree and buff with very fine Scotch Brite. (000). (I have not been able to find any but "fine."
Apply more Breakfree and allow to sit untouched for 24 hours.
You don't really need the heat, although I suppose it won't hurt. I've used Oxpho-Blue on an entire frame, and on a 1911 slide. Neither looks like they came right out of a restoration shop, but both came out MUCH better than I ever expected. And I've had no problems with rust. For touchup, I just use a Q-tip, then wipe dry, then burnish with 0000 steel wool, according to the instructions. For touchup I don't bother, but for the frame and slide I used white vinegar as a neutralizer after applying the bluing, to stop the rusting process.
The only thing I wouldn't do is used steel wool to actually apply it. It reacts quickly with the steel wool and what you end up applying seems to be some sort of mostly inert liquid. Use a cotton swab or cotton ball or maybe a piece of cloth in place of the steel wool for application. I would do the buffing with the 0000 steel wool between applications of the cold blue and also do the final buffing before applying oil. The degreasing isn't really necessary but makes things work a bit faster. If you're used to messing with cold blue, you'll never go back after trying Oxpho.
Bluing creating rusting: I've had occasional rust issues with cold bluing of all types. I try to avoid it except for touchup for that reason. You may have bluing salts creeping out of pores and causing the rust. You can either buy bluing neutralizer from Brownells or somewhere, or try using baking soda water to neutralize it, or perhaps household ammonia. If you neutralize it, be sure to rinse it well and reoil thoroughly.
Also re creating rusting: Try a vinegar, (white), soak to neutralize any active solution. You will have to remove the oils from the surface first to give the vinegar a chance to penetrate to the metal.
http://www.gunsandammomag.com/techside/blue_0515/
I always have a bottle of Brownell's Oxpho Blue on the bench for touch ups. I found applying it with a little dab of 0000 steel wool makes it come out darker and it blends in with existing factory blue. It's the only cold blue I've found that works on cast just as well as regular steel. For small parts such as screws, I pour a little in the lid and drop the parts in for a few seconds. They turn totally black.
I degrease the parts or the barrel and use a heat gun to get the part very hot. It blends pretty well with the hot blued guns that are the black color, but it won't match worth a flip for any of the slow rust blued guns. I use a cotton ball to apply it and I let it sit a little longer than a minute, but make sure to keep the part wet with the creme. Do several treatments to get the dark color your looking for. If the gun isn't very dark, it should only take 2 times of wetting the metal, more than 4 to get it to match a newer gun. I apply Breakfree afterwards and buff it good with 0000 steel wool. I then wipe it clean and reapply the breakfree and let it sit for a day or two before handling the gun. Good luck with it.
The key for it working well is localized heat and removing any oil, even though the directions say you do not need to degrease the parts to be blued....
I had some very fine Scotch Brite (000), which I tried on some case necks instead of steel wool. The Scotch Brite material worked great. The more I wiped the steel lightly with the Scotch Brite pad the deeper and more uniform the blueing became. As the Scotch Brite shined the steel, it blued the freshly cut steel to a very dark and uniform finish. The instant blue on the new handle looks as good as the blueing on any other Redding parts. Now I have made a Scotch Brite Q-Tip for my various blueing needs by hot gluing a small piece of Scotch Brite onto the end of a Popsicle stick.