I use the standard brass rod from my welding supplier. I get the smallest rod they carry (3/32"?) 'cause it is easier to work with. I get bare rod and a can of flux but you can get prefluxed rod too. Whatever spins your prop. If you go with bare rod, get a can of their standard brass brazing flux. It will last through your grandchildren's lifetime.
If you aren't used to brazing, practice a little on a scrap piece of steel. Set your torch like you would for welding steel except add a little more acetylene (slight blue tail off the tip of the inner blue-white flame). Important to have the flame reducing (gas rich) rather than oxidizing (oxygen rich). Heat the rod and stick it into the flux so some sticks to the rod. Heat the steel to just below red-hot and start to feed in the brazing rod. If you get the steel too hot, the rod will sizzle and burn into the steel which gives a brittle steel/brass alloy that isn't good. Very weak, porous, and ugly. If the metal is too cold, the brass will stand up like a wart and not adhere very well or simply melt and roll off the steel. When the conditions are just right, the brass will flow out over the steel like ranch dressing on a salad. You can then smooth it out by playing with the flame. Done right, there is very little finishing needed.
You can tell you have too much acetylene in the flame if the brass puddle bubbles like boiling water. Too much oxygen 'burns' the brass and it acts like over-cooked bacon in a frying pan.
If you are comfortable welding steel with oxy-acetylene, you can learn brazing in a few minutes. Same torch techniques, just different gas settings and heating/puddle control techniques.
Forgot to mention that the steel needs to be bright white clean but that is no different from the spec for any type of welding.
[ May 15, 2003: Message edited by: firstname.lastname@example.org ]</p>