Do you have a rosebud tip for your oxyacetylene outfit? It generally
works much better that a regular welding tip for preheating. Even if
you gas braze, you could probably preheat with the rosebud, quickly
swap tips, and fire up the actual torch tip. The rosebud that I am
familiar with is an entire section like a cutting torch attachment and
not just a tip, although they may make a tip attachment also.