We do lots of sculling drills, the swimmers soon learn they go much faster and easier with the wrists cocked instead of straight. This first hunch when done correctly will put you in a butterfly position and will utilize the large latissimus muscles of the back. These muscles are stronger and have more endurance than the forearm muscles. The second hunch begins with the insweep. As the hands scull inwards under the face, the shoulders hunch up to narrow the body as the kick begins and the swimmer stretches out into the streamlined position.
Timing is what wins and loses races.
I tell my swimmers, kick, streamline and fast scull. But I also tell them that during a race the hands are actually beginning to scull outwards during the streamline and first hunch. This is called overlap timing and is used by all championship breaststrokers. Breathing should be done during the in-sweep scull. The force of the hands coming inwards lifts the body up out of the water.