Very rarely do you ever run into a movement that can be used to both demonstrate and build strength at the same time. One example is the static hold. You can use dumbbells, kettle bells, or buckets of sand like shown in the figure below.

The Marine Corps and martial artists have used static holds as a shoulder strengthener for years. You could add static holds to your workout after your overhead pressing is done for the day. A single 30-second set should do it. If you get over 35 ticks, add two or three more pounds of sand or gravel to your bucket. Then shoot for 30 seconds.

Static holds are great for the grip, delts, and your concentration. Just be sure to pad the handles to save the old palms.