It really depends on the pattern of Twist finish you want to replicate. If its a wide band pattern, then use tape or strips of cloth, etc. leaving a gap between the strips- or "stripes" so that you can finish the barrel with browning solution in between the strips. If you want a narrower pattern, then use jute, or some kind of rope or string to wrap around the barrel, and set your gaps between the strings, to create that pattern.
There are several ways to do this. Assuming you want the barrels to be browned, apply browning solution to the exposed areas, leaving the tape or strips in place to protect the covered areas. You can card these exposed areas and then repeat the process, to get a dark color to the barrel there.
Then, remove the tape, and brown the whole barrel again. The area already browned won't get much darker, and the Now newly exposed area can be browned to a lighter shade of brown. Stop the browning process when the barrel looks the way you want your replica twist finish to look.
If you want the barrels blued, or black, you can use the same approach or technique, but substitute bluing compounds, or if you want a rust blue/black finish, then rust brown the barrel first, as described above, and then dip the barrel into a trough filled with boiling water to turn the rust brown to blue/black. Card the rust, with coarse cloth, and put the barrel back into boiling water again. Repeat until you have the color of black you desire.
Some time back, a picture appeared on this forum where someone use tape to mask a pistol barrel, and he used a razor, or exacto knife to cut slits, and patterns in the tape to expose the barrel. He then browned the barrel with the tape on, to protect part of the barrel, and then removed the tape to finish the browning.
The barrel came out in a camouflage pattern that was surprisingly beautiful. This is different than traditional damascus barrel patterns, but it was nice to see someone try something new/old.
I think you will get the best LINES to separate the stripes in the pattern if you use tape on the barrel, rather than rope, or string, or cloth strips. The other materials will give you "fuzzier" lines.
Try these on a piece of scrap metal, to see what you like, before doing a barrel. The barrel can be polished bright again, of course, and redone, but why go there if you can determine what you really want before deciding what to do with a barrel?
