Well, I don't know what teaching method you seek. I 've been teaching myself and not with a book. For instance - I practice Balkan Brass folk sounds for the most part,in order to practice that music/create improvisations you have to have a grasp of the true nature of that music - the dynamics/ and the scales( klezmeric and balkan folk music use a unique type of scale build up).

Essentially all you need to do is listen to the music style you want to learn, you listen and listen to it some more, you try to play the same tune on the horn - once you understand how a certain style of music sounds like , all the dynamics and improvisations will follow a distinguishable pattern.

That is my method - it's working for me. The thing is I believe that being taught by a teacher isn 't nearly as effective as discovering things on your own. The joy of discovery (also knowing that YOU discovered it for yourself) is encouraging.