I would add that you can get at that pec minor pretty smoothly against a wall using a lacrosse ball. Operate near a corner of the wall, so you can put your head past and really lean in as much as you need to. 

Check out a bunch of pictures of the pec minor online if you’re not familiar with where it’s located. It can be tough to single it out and know that you’re hitting it beneath all that big meat of the chest, and having a strong concept of what it looks like sitting on the ribcage has really helped me.

Good luck!