When I worked at Synchros in the late 80's I used a fine tipped oxy-acetaline torch to braze cantilever bosses to fork tubes, fix broken bike frames, build handlebar stems, and whatever. The extreme heat and pinpoint focus made it about as easy as applying hot glue. Easier once I got the hang of it. I learned on the job. And so far as I know, no one died as the result of my handiwork. These days I don't want to deal with big rental tanks and such, as I have just a 9.5' square shop (if you don't count the huge and awkward built-in shelving area over the entry stairs, which make it more like an 8' x 8' shop if that) and every square foot is accounted for. Big gas tanks, no thanks. So I use a BBQ propane tank from CT and one of these, also bought a bunch of years ago at CT:
For years before that I used a two-tank solution (yet another CT purchase) with propane and oxygen, but the valves were tricky and the oxygen ran out WAY too fast for its cost, so I went searching again and found this one. And it works better. Must be in the porting, as the air blend seems to be just about perfect. With an even older torch (something-Jet, also from CT, bought in the mid-1980's) I almost melted the flow control brass spacer trying to get stuff hot enough if the steel was anything bigger than a finishing nail. With the two-hose, two-valve, two-tank setup I'd spend half my gas just trying to dial in the flame. With this BernzOmatic thing I just turn it up slightly, spark the flame, crank the valve open wide and let go. Anything as big as a few ounces or smaller heats up in a minute or less and provided I've prepared the surfaces well (wire brush, sanding, grinding, whatever) and melted on some of the rod's light green flux coating (I'm still working my way through a tube of brazing rods bought at CT over a decade ago and they're still fine) onto the steel roughly in the area I want bonded, the bronze will flow nicely when the steel on each side is a bright, almost peach orange. Cherry red isn't good enough.
I'm not sure I'm the best guy to explain brazing. It sort of seemed I was a natural when I first picked up a torch. The brazing guy in the shop where I'd just got work, Synchros (mountainbike stuff), one day got frustrated trying to mend a broken, rusty chainstay on a neat old road bike. After half an hour over-heating the steel he gave up, mad as heck. I asked if I could give it a shot. I hit it with a wire brush and file to clean up the mess he'd left, brushed on some of the paste flux the boss said to use, heated it with what seemed to me a good pencil flame of a good blue (don't ask me how I knew), and flowed on some bronze. First try.
And it's mostly just gone like that for me. Somehow soldering is my nemesis, but brazing is easy. Guess I like higher temperatures or something. But it's really easy if you have the metal somewhat clean and get it hot and flow some flux onto it. I introduce the rod (the part now cleaned of most of its rosin by transferring that to the steel) when the steels are glowing nicely, get the bronze glowing almost as brightly in the flame while keeping the steel really hot, then touch it to the steel. And it flows. You want to 'pull' the bronze, not push it. Let the heat bring the bronze towards it, don't use the flame to push the bronze into the crack.
Don't over-heat the bronze once it's flowed. It's easy to boil it and compromise strength if you're using a proper kit. With this budget (about $38 maybe 5 years ago) kit it's hard to get it too hot. Make sure your tank pressure isn't running low, as I find the last 1/4 tank or so makes it challenging with larger chunks of metal. Wide open on the valve, or close to it. About 1" to 2" from the tip of the brass nozzle, you'll have to judge that part as you go, playing with spacing until you get it heating fast. Speed is important.
As you can probably see from the picture, my braze on that barrel nut wasn't perfect. Some bubbling. It was a big thing, and I was brazing stainless tubing to some unknown carbon steel. Many will say that brazing stainless is a no-no, but that's nonsense, it works fine. Sometimes. It's easier to mess up stainless joints, but if you're fast and the work's clean it should stick nicely.