I have struggled with this for a long time as a former asymmetrical throwing athlete. Kait’s on point about the push-up diagnostics, and the use of a slingshot. I made my a loop with a weak theraband to encourage proprioception in that region during the push-up and it has helped a lot. One thing that has helped me is inverted rows concentrating on internal rotation and a pause at the top of the maneuver. Feels unnecessary to the uninitiated but after a set take a look at your resting scapula posture. I found it really flattens the blades to the rib age and encourages the coveted posterior tilt as well. All that being said–one night of sleeping weird on my side will have me revert back