I`ve been off a long time now with my Colitis and shoulder issues. 
Both shoulders feel Ok now as yet are untested in the gym but I`m gonna` attempt to make one of my many hundreds of comebacks. LOL 
I'd never presume to advise the man who invented the barbell on the Serengeti plains with a branch and 2 rocks, but years ago Coach told me to hit the external rotation work like I meant it. Knock wood, things still seem ok. AthleanX on Youtube has some great vids, if you haven't discovered him already.
Here's to a kick ass 2019, tough guy!