I have that book and his straps as well.
The book is two parts, one about accordion technique generally from Jacomucci, the other about AT applied to musicians from Delaney. I haven't worked through all of it yet. The straps are odd, but the hip belt is a real game changer for weight distribution.
I recently realized I am almost always tense. My bayan teacher pointed this out when I started taking lessons last year. I gave myself tendonitis in both hands after a particularly intense couple of days of practice in October. I am about 90% recovered and have slowly been getting back to playing. I have had a few AT lessons with a local practitioner to try to learn to avoid reinjury. The general gist seems to be learning how you move your body in strain-inducing ways, then relearning how to do them in less straining ways. Pretty hard to do, in my experience so far.
