Reggie... I am no great shakes myself, but I believe that the fastest way to improve is to play a lot, and to listen to the masters of the instrument like Terry, Rice Miller, Norton Buffalo, and others mentioned in the above posts. The key to improvement for me right now is increasing my control over alternate blow and draw notes along the scale.Steve...I think the "overblow" technique you mentioned may have to do with creating a secondary tone by blowing extra hard on a hole.
LEJ