That's a good question. There's other pressure points as well
   that should work just as well. For me, massaging between the
   thumb/finger worked just as well and it's more accessible.

   But yeah, that's a very good question. I mean you *should* be
   able to access the muscle to get the knot out ; maybe you could
   go at it from the opposite:

   push your chest forward and shoulders back. then pull your
   elbows straight down as if you were trying to shoot an aircraft
   out of the sky with your chest.

   [best way I can think of to describe the movement]

   It's a stretch that seems to unravel the knot in that muscle
   spot, at least for me.