What is the correct driving technique when descending a long, continuous steep mountain slope?

1. Shift into neutral (N) or depress the clutch to coast and save fuel
2. Turn off the ignition key to allow the engine to cool down while descending
3. Select a lower gear to utilize engine compression braking (利用发动机牵阻制动), and use the foot brake intermittently only to assist speed control
4. Apply the handbrake firmly and keep the accelerator pressed