The "bus driver" exercise is where you hold a plate at arms length in front of you and rotate slowly. It's a hugely underrated movement. It's an excellent way to finish the shoulder workout and make the joint more resilient to injuries.
Start with a 10 or a 25 and work your way up to 45 pounds.
Learn to apply force quickly and it'll make you stronger. That's what speed training is all about: power, explosiveness, and strength. Try this before you plateau.