Using your protective gloves, submerge the bottle vertically, open side down, into the hot water until it completely covers the score line. Hold it in the hot water for 5 seconds, and then immediately submerge it in the cold water. Hold it in the cold water for 5 seconds. Repeat this process until the bottle separates at your score line. You will hear a small "pop" as the sections separate.

I wasn't able to take a photo of this step since my hands were both occupied, but attached is a photo of the final result.