I concur, shoulder and back work is one thing that helped me open my chest up more than anything else. Even just hanging on a set of rings for a minute after sitting for a while feels really good.
Totally, dead hangs are amazing. I have a pull-up bar over the door to my office and will just hang there for a minute from time to time when I'm walking through it. Wish I had the space to mount the rings I have inside though!