Brazing for hobbies

You should use solder, not brazing. Brazing is used to join iron or steel products together.

brazing clints head

Brazing is also known as soldering or soft soldering in the layman vernacular.

You usually do not braze copper, you solder it. If you were to use brazing rod on copper, the copper would have very close to the same melting point as the brazing rod. This makes it difficult to do. As far as preheating the copper, it needs to be hot enough for the brazing to flow.