When brazing horizontal joints, it is preferable to first apply the filler metal slightly off-center at the bottom of the joint, proceeding across the bottom of the joint and continuing up the side to the top of the joint. Then, return to the beginning point, over-lapping slightly, and proceed up the uncompleted side to the top, again, overlapping slightly. This procedure is identical to that used for soldering.
Also, similar to the soldering process, make sure the operations overlap. On vertical joints it is immaterial where the start is made. If the opening of the socket is pointing down, care should be taken to avoid overheating the tube, as this may cause the brazing filler metal to run down the outside of the tube.