Very difficult, jinxed, lets say its hermetic. May be only in the beginning. The button lay out wasnt made for students, is was designed to provide fast runs (right side) and knotted cords (left side). May be you know already, but the bandoneón wasnt invented for tango, nor made for folk music. It wasnt invented in the Ore Mountains between East Germany and Czechia, too, as you always can read. It was invented for church music and chorals in the coal mining districts of western Germany. A pedal harmonium was much to expensive for the small reformed parishes, so an organist invented a cheep alternative, and put it into the frame of an accordion. This is the reason why accordion and bandoneón sound differently and are so totally differently built inside, but on the other hand bando and harmonium share the same reed tongues and zink plates. The production of the new instrument was translocated to the AA-manufactory in East Germany, then. And thus the name changed from Bandonion to Bandoneon.
Starting: The opening left, the opening right, the closing left, and the closing right all have a different button allocation. They are not symmetrically laid out. So you have to learn 4 instruments. As in tango dancing the first 2 years are made off getting theses patterns into your cerebellum. The next step is to play little melodies so that you learn to change from opening to closing, it means you learn to combine 2 of the 4 instruments. The same on either side. The next step is to combine left and right instrument, and so on. In the end you are able to play little folk songs. And that is how far I am. To come so far you do not really need a teacher. But to learn tango you actually do (air management, fingering, marcato, staccato). I have really talented players around and luthiers among my friends, but what about you? The crowd isnt that great. Try to find some contacts within the bando list. Good luck.
Additionally, not everything that looks like a bando really is a bando. There is a small brother, called Chemnitzer. Inside bando an chemnitzer are identically built, but the button lay out is different. Mostly Chemnitzers are more colorful, but this isnt always the case, so beware not to buy the wrong instruments. Chemnitzers are really wide spread in America, actually more than in Europe. As the bando became simply the tango instrument, the Chemnitzer is the Polka instrument within the szech and polish communities in the midwest of the US. A lot of bando players have a chemnitzer as a resource for spare parts, because they are not that expensive as a bando.
