Good brazing technique involves a lot of factors. I'll mention some basic ones here. First position your 2 tubes to be in a V with both sides at an equal angle so when the brass melts it runs into the valley. You control brass by keeping it in the mushy temperature state between being liquid and solid. If you heat it just a nanosecond too long it will run away. This need for precise control is why you use compact hand motions (newbies tend to move their hands way too much). I prefer to lift my rod slightly off of the puddle. Most likely your rod and flame should be at roughly a 45º angle to the work. The most dominate method of heat control (there are a number that influence) is by flicking the flame on and off the puddle. If you were to watch Herbie or me demonstrate in class it doesn’t look like we are moving either hand all that much. When you have filled the valley you need to move the joint so as to always keep the puddle on top.