One theme that will appear repeatedly on this site is Economy of Movement
The positioning of the right hand is crucial to playing the Button accordion correctly. Few Tex Mex accordionists
use the thumb strap. It is more common to anchor the thumb along the edge of the accordion. The less movement
of the hand, the better.
The right hand should be about half way down the buttons with the thumb anchored at about the one quarter point.
Find a comfortable position and try to move from the wrist or by extending the fingers. Note: For some styles (Vallenato)
it is common to wrap the thumb around the back of the button area. This would slow you down in the Tex Mex stlye.