Oh... Another thing that I would add: Do a lot of work on building up your core strength. This makes a world of difference for (not only) fast kicks and also powerful kicks. Being able to generate a lot of torque between the rotation of your shoulders and hips is a must for powerful kicks.
It doesn't matter if you agree or disagree
... As long as I don't bore you and I spark a moment of thought, my goal is achieved
Queng leon queng tigre ecu tacacut, queca pa? - Pampangan Mandarigma Motto