Back in the early days of interweb and forums/email lists an early Trek builder was a contributor, sorry but his name escapes me. He described some of the brazing methods they played with to speed up the process. Two torches was done both by two people and just one. The two people efforts did take a bit of coordination between them and but for needing that second set of hands and eyes (added labor cost per frame offset the faster work) they might have continued it. Now I was more interested in the one person and two torches and their mouth held the filler rod (where was OSHA). The mental image was nearly funny.

I've tried two torches myself but I made a torch stand (along the lines of a microphone stand) and that second flame really needs to be moving about if you're using a normal tip (and it's very concentrated flame), perhaps a rosebud flame might not produce a too hot spot too soon. I've also tried this with a simple propane /air torch (hardware store cylinder) when removing dropouts and for this the stationary flame works better but is hard to keep aiming where you want it as you play with the hot dropout/stay unit.

By all means do play with a second flame, safely please though. I found myself forgetting about that second flame at times and could have bumped it or burned myself if I wasn't careful. How you set up the torches and joint to be pulled apart is important, I'll add a weight (hanging from a wire or vise grips clamped onto the part that will fall down after the filler is completely liquefied. Andy.