If recoil sensitivity is an issue then a muzzle brake might actually cause you to flinch more than you did before. It may kick less but the blast you feel on your face is going to be significantly higher than you expect. And yes I will agree with everyone else, you can hurt your hearing after only one shot.
You would be better served by putting on a better recoil pad or going to reduced power loads. The .300WSM is plenty powerfull enough where you can tone it down and still have more than enough gun to kill.