I went to welding school and got a TIG welding cert. I practiced a lot and thought about bikes all the time and raced a lot as an amateur and accepted work job welding frames for start-up ventures. I liked what I was doing and it happened to be what was popular at the time making it lucrative. I was lucky with getting a bike job but a lot had to do with having a specific skill way in advance.
Personally, I would master the craft that was of my interest and then apply it to bikes. If hearth brazing is your interest, they do it and apply it to bikes either through a course or your own diversion. If hearth brazing bike is it, then find the path that takes you there. That may very well be a bike course with someone who knows that technique or a hearth course? do they exist?