So say I wanted to squaring a 4 foot section of pipe, what would be the
best way to heat the entire section? Hmmm, I guess annealing 1'
sections and then welding them together would be doable, although time
consuming.

I just got off the phone with Weld Mold. They make SMAW electrodes for
tough pitch copper and their technical person seems to think it would
be fairly easy to weld the copper bar using their 4333 electrode with a
pre-heat of around 500 degrees.

So if brazing doesn't work, I might just try their rod. I'm feeling
pretty confident that I can get this all worked out. I'll probably
start working on this project in the next two weeks and will give a
status report then.