I don't like the doorway stretch because I lose all circulation in the arm. Instead, I lay on a wide yoga bolster (with the addition of a buckwheat pillow on 2nd bolster to get enough length for my back). I then drop my arms to the side in various positions. The one that catches the pec minor the most is with the arms up. I can really feel it.

It's also a total "gravity stretch". You don't do anything except relax as much as possible because you are laying down.

You can do variations like arching over a large exercise ball, or letting the arms drop back when you're 45 degrees back on an inversion ball.

It took time for my pec minor to lengthen. Several weeks of doing the pec minor stretches twice a day.