1. Get left hand ready and lower the whammy as low as possible.

2. Pinch the G string and.. wait.. lol, G string.. ok anyways, pinch the G string and gradually let the whammy rise with your left hand.

3. If you have bad sustain, pinch again and as soon as you pinch the second time, lower the whammy just a little bit but do it swiftly and then let it gradually rise again.

4. Try alternating the string pinching! Hope it helps and good luck!