The small torch you describe isn't hot enough to do an adequate job.
You really need oxy-acetylene to braze larger objects.
Also need to use a brazing flux to make the brass flow. Common
household Borax will do in a pinch. Heat the end of the rod and dip it
in the flux before brazing.
It is a pretty simple technique; the same as soldering except with a
higher temperature.
Good luck, Bugs