I really think we should do a unified 'shoulder pain thread', almost everyone gets it, and for some reason, even more so at the moment.
Anyway, what quake said about scap retraction/depression is perfect. It's a must, at all times, if you are prone to popping/pain at the shoulder joint. Remember that imingement likely occurs due to muscular and postural imbalances, as well as predispositions like the bones' structure.
However, one issue I have realised recently is that I (and others) who are predisposed to shoulder pain have a far greater mind-muscle connection with upper traps than low/mid traps. This makes the issue worse, as when you think you are depressing/retracting you back, you may be contracting upper traps. Foam roll the shit out of upper traps on alternate days. The rest day is paramount. I have a trigger point map for shoulder pain if anyone wants it.
Also, work rear delts, low/mid traps and rhomboids with good contraction, physio-band style at first. Only stretch chest, triceps and shoulders in a way that allows you to do it scapretracted/depressed, otherwise the seemingly-harmless stretch will hurt you.
I tried taping to inhibit upper traps recently, works beautifully, promotes proper posture (at least in the short term). Tape from acromio-clavicular area, over the upper traps, down the midback, so that the two pieces of tape (from the two sides of your body) intersect at T-6 or thereabouts) on your spine.
I would also chill on chest flyes of any sort, at least for now, as these have the same effect as the stretching (if not cautious, they will fuck up your shoulder). Chest flyes are basically loaded stretches.
The diesel crew thing looks okay, but honestly, it looks like it was designed for somone who isnt injured. There are many movements whic could hurt someone in your position. There mustn't be a 'one-size 'fits-all' approach. The main advice i'd give is:
IF IT HURTS (YOU) DON'T DO IT. Whatever the movement may be, leave it alone. Do what you can, and i'm sure there's lots more advice you can find in the search box. Hope that helps for now. Good luck mate.
PS also watch how you sleep, please! Lie on your back, and don't fidget. Lying on an injured shoulder is not a good idea.