Student or Learner
Pull the brakes.
No, you have to keep your hands on the handlebar. Reach for the brake with your four fingers while keeping your thumb in place. Just squeeze the brakes gradually.
Not a teacher.
Squeeze is OK - better than pull. I'd use "apply the brakes", given that, when confronted with a bike brake, there's little choice of what to do. You can apply it, or release it.