Regular lateral and rear raises are great for enhancing the shoulder muscle area. The variations I will mention are something you have probably never encountered. Try them and see how effective they are. Try holding dumbells, weight plates, or kettlebells at arms length in the crucifix position for time. As this is progressive overload training , you increase the time or weight to make gains in strength just as you would in normal range of motion training. Try holding a set weight for 1 min. I would do at least 30 sec. and 1.5 min should be the longest hold. If you can do this increase the weight.
Another variation is to use way heavier than normal weights for your laterals or rear raises. This time you will only be doing a partial movement from the bottom (start position) . Go as far as you can and HOLD for time as in the example above. You may only move the weights about a foot or so from the starting position. You definitely have to try this….. it works! You get a phenomenal contraction in the involved muscles. I would do 2 -4 sets of 30sec. to 1.5 min.