This advanced version should only be performed by Green or above ranks. For any air version of the technique at lower ranks, stopping at the shuto is adequate.
Watch this video to see how to properly build your hook kick. This is a very challenging kick to develop, but once you have it, it’s a fantastic weapon. Pay attention to which muscles you feel when you’re working the kick. You should feel it in your glutes and obliques if you’re doing it right!