[Alfred]

Try Playing “Let Her Go” By passenger with Barre chords. Not the whole song at once, but parts of it throughout the day or once or twice a day. It is a standard progression and will at least get you transitioning from the E and A shapes. You can call it musical thumb exercises 😛
I still wouldn’t want to play a whole song in nothing but barre chords on an acoustic. well maybe if I had my action as low as possible, but then I couldn’t dig in to the guitar and howl without a lot of buzzing.