Having had and later found ways to avoid the same problems for decades, I know you're on the right track:
-No lower than 8-10 reps/set, and no more than 1 minute rest between sets. Doing this, you can use normal speed for each rep, or can use the super-slow method you've described. Moderate reps in the 8-12 range are best for growth anyway, and remove the amount of stress. Adjust the reps upwards or the rests between sets downwards to further reduce stress as needed.
-Avoid any exercises that are inherently tough on the shoulders. Instead find good substitutes that include the possibility of using cables and machines. The effect varies by machine-some are better, some aren't. Include any calisthenics that work well without creating joint problems.
-Order the exercises so that the more stressful ones are done as the 2nd or 3rd exercise, after first using exercises that don't hurt the joints and further warm up the area.
-Do any cardio or other general body exercises prior to lifting.
-Intensity techniques can increase the desired stress on the muscle while using less weight and thus reducing joint stress. Compound supersets & trisets and negatives are examples. Pre-exhaust would be another, as would partials and rest-pause. Partials can be used in two ways-at the end of a set after reaching failure, or doing full sets of just partial reps that are 50-90% of full ROM. Takes some experimenting; for example on preacher curls eliminating the top and bottom 8th of the ROM helps in two aspects. Stopping before the very bottom will avoid ligament stress around the elbow while at the top it will keep stress on the muscle. With squats, a 50-60% ROM with bench squats can be easier on the knees.
-Don't work out in cold temperatures; if you do wear extra layers of clothing.
