In e.g. Wing Chun you jump out of your skin and stick your arm in front of your face, elbow in the air, hand about face height. They call this Bong Sau.The beauty of it is how this natural response to fright is converted to the defenders advantage, by practising flowing into other techniques from this position.
If you see agressive hands before they are launched you reach out and trap (control) the hand, or brush it away.
As such the idea of defending against a punch is not really in the CMA mindset. You defend against /redirect certain types of force from a certain direction, and convert into an attack.
You see examples of attacks which the forms are supposed to defend against, but the forms are mostly examples of good movement which can be used to throw, sweep, strike or lock within the same movement.