Pin and stretch type soft tissue techniques are very popular. Early on in my career I used them to great success along with great discomfort! However it's a fallacy that with great improvement comes great discomfort (with manual techniques).
This along with a Lat Positional Inhibition are two great ways to improve shoulder ER and overhead mobility with little to no discomfort. Make sure to follow this technique up with wall angels/slides or repeated shoulder extension.