As a 4x4 instructor we always taught that the parking brake should be applied with the button pressed down to avoid wear on the pawl. However, the parking brake should not be applied until the vehicles was stopped and resting on the gear, either first or reverse. It should always be called the parking brake not the handbrake as it should only be used when parked or stationary. In addition when entering the vehicle the very first thing that you should do is to put your your foot on the footbrake this reduces the possibility of vehicle runaway if on a slope and the parking brake is not as good as it should be. Interestingly, on the latest Defender it is advised in the handbook that you should hear the clicks as you apply the parking brake.
John Channel
John Channel