I'm sorry, I said Gatoraid bottle, I actually use a wide mouth Nalgene (orange so I don't get it confused with anything else). I intend to try the gatoraid because it would be lighter. With the Nalgene, you have to keep the mouth of the bottle pressed up against your body at the right spot. Practice in the bathtub. I've gotten to where I can do it by feel without a light.
Bookmarks