In terms of strengthening the shoulder, there is no avoiding the value of rotator cuff exercises. This particular exercise increases stability in and around the shoulder joint critical for the protection of the joint during most athletic activity. It involves active work on the way up with the pull, and negative resistance work on the way down in the controlled motion. A TRX can be found at this link.
Using a TRX this focuses on using bodyweight to train for muscular endurance and stability. This exercise benefits the core, the shoulders, and the chest. The important factor in this is to keep the core engaged so that the body doesn’t wobble during movement. A TRX can be found with this link.