A plain fuel torch, be it propane, butane, MAPP, or gasoline, fuel, is not really suitable for BRAZING work. Now then, I'm sure there are some minor exceptions, but I stand behind my assertion!
If you can live with silver soldering (also called silver brazing, now), that is different and doable with a fuel-only torch. The fit-up requirements are more stringent for silver soldering, however.
The HANDY AND HARMAN definition for the various temperature ranges for joining is as follows:
Soft soldering (typically plumbing, electric, electronic, 400 to 700 deg. F. Silver soldering, 1100 to 1500 deg. F. Brazing, 1600 to 1800 deg. F. Welding, above 1800 deg. F. (with the exception of aluminum)
A fuel-only torch would have a difficult time holding an exposed work piece at 1600 deg. F and above, which is a cherry red colour. If you were to enclose the work piece in insulating material that would change things; but heating it up with a torch in the open, applying filler material in the open, would be a frustrating experience.
To a large measure it depends on the size of the work you wish to do. For jewellry sized work brazing with fuel-only torch may be OK as stated by others.......anything larger....model engineering sized....would require oxy-fuel for satisfactory brazing.
Trust this helps a little.