Oscar was brewing his own rusting solution. I had a supply and used it on several guns with good results. When I ran out of it and Pinkertons I tried Brownells and found that it was much faster here in LA. Our very high humidity makes it work in a couple of hours. I would point out that Oscar was using log wood dye as a treatment after rust blueing. That dye is available as a liquid trap dye so you don't have to buy chips to make your own.
bill