Thanks folks,
The "twist" finish is easy in concept but tedious in execution. I studied many photos of English twist and stub twist barrels and selected a Manton pistol barrel as a model. I polished the barrels with 1500 grit paper and degreased them. Then,using the Manton barrel as a guide, I carefully painted the inverse of the pattern on the barrels with etching resist (standard asphaltum ground from jewelry suppliers). I practiced a bit on another barrel to develop the skill to mimic the real pattern. I used several brushes of different sizes. Once the ground was painted and dried, I sealed the muzzle with a cork and painted it with ground and then painted the breech plug. I placed the barrels in a glass baking dish and covered them with Ferric Chloride (circuit board etchant sold by Radio Shack). I soaked them for 30 minutes, then washed with water and again with water and baking soda. The resulting pattern was beautiful and could be used as is with no browning. In fact, if you just apply cold bluing to the barrels and sand it off the high spots, the result is spectacular. Next, I browned the barrels using Dixie's browning solution, which produces a much redder, coppery color that any of the other solutions. I carded the barrels using 1500 grit paper wrapped around a block of wood to remove rust from the high spots but keep the color in the low spots. After getting a light coppery color, I washed the barrels in water and then put them in the oven at 475 degrees F to deepen the bronze tones. After that, I rubbed beeswax on the warm barrels and buffed them. The brown may not turn out to be really durable but it doesn't matter because the underlying pattern is really nice without any browning and as it wears they will assume a nice old rubbed patina. Before choosing this method I experimented with a number of techniques. I can tell you emphatically that painting the whole barrel with resist or some other coating and then scraping in a pattern is a waste of time. The resist doesn't scrape away cleanly, it is hard to follow the pattern around the barrel, and it almost always looks too machine like to be real.
dave