You might try an electric soldering machine. I’m not talking
about a Sparkie or Fusion welder, but an old-fashion electric
soldering machine. Although its been years since I’ve used one, I
believe they are still available and really reasonable in price.
After a little practice, you can get the solder to flow so
quickly that its almost instantaneous and any firescale etc. is
very localized. Its essentially a small carbon welder, and I’ve
seen people do amazing things with them.