One thing to keep in mind here is that benching is only a piece of a very intricate puzzle when it comes to the throwing shoulder. If you are going to bench you may want to look into incline benches and keeping your elbows a bit closer to your body then normal. Most guys bench with their elbows straight out to the side which puts alot of pressure on your shoulder, instead bring your elbows in just a little bit tighter to your body.
Now for the big question... What's the most important part of an Indy Race Car? The engine or the brakes? The key to gaining velocity in your arm/shoulder is the ability to apply the brakes after you release the ball. Your body is a very cautious machine and will not allow you to throw harder then you can stop. Be sure to work the muscles in the back of your body (lats, traps, rhomboids, posterior delts, external rotators, etc.) at least 2x as much as you work the muscles in the front of your body.
Next piece of the puzzle is the ground. All or the force produced in throwing a ball is generated from the ground up so make sure that you have a very solid foundation in your legs, especially your hamstrings and glutes.
But strong legs won't get you too far if the power is lost in your core. Remember, the chain is only as strong as your weakest link so make sure that your core is a solid link between your powerful leg muscles and your smaller upper body muscles. Train the core with flexion/extension movements, rotational movements, diagonal movements, and lack of movement in stabilization exercises.
The throwing shoulder needs to be cared for and prehabed, but is the final piece of the puzzle when it comes to throwing strength/velocity. Work from the ground up and from the back to the front and you will see great results!
Yours in Sport!
Coach Dan