I too prefer the look of blueing and have had very good success with blueing the barrels on a beretta......but unfortunately not on a Cooey. As mentioned in another post, not all metals will take to the cold blue as well as others. I suspect you may not have very good luck with the cooey either, however, its not an expensive deal to at least give it a try.
The key is to not skimp out on the prep work. Hands down that the most important part. The success I had with the Beretta barrels was a direct result of all the work I put into the prep. The actual blueing process was the easy part. I will also suggest that if you are going to do this over a couple days, depending on which product you are using, you may need to lube the parts before setting it down for the night. Some products like Birchwood Casey super blue will flash rust overnight if not oiled (however G92 does not), and you will literally have to scrub rust off the next day. The beretta I completed got about 6 coats of blueing, and between each coat, the barrels got another good scrub down with degreaser, and a light sanding with steel wool. The sanding with steel wool really helped with each coat of blueing added. The majority of the original blueing was already gone, but I did not remove the factory blueing that remained. The steel wool between coats really help blend the old and new blueing to the point where it was not visible to the naked eye. Once you are completely satisfied with the work, make sure you put a light coat of oil over the entire blued area before you put it back into the safe. Im no chemist, but what I noticed over time was that the oil impregnated into the steel barrels and eventually with a nice solid buffing, the barrels attained a more polished and darker blueing then it previously had. I eventually started using a Birchwood Casey product designed as a coating for rust protection and the barrels looked almost flawless. I was actually very shocked how well the whole project turned out....i really didnt expect much when i started the process.
However, back to the Cooey....nothing described above did anything for the 64B I tried blueing. It didnt look any different coming out of the project then it did going into it. The same steps, prep work, products, and elbow grease.........and nothing. Im not sure if you'll experience the same thing, but I figure it was an important point to note.
