KMD posted a very nice short video on how to dump gas while riding a scooter.
In his words:
Some items to notice.
* By thumbing the light the diver keeps it pointed forward into the view of her buddies and frees up a hand to manipulate dump valves
* The divers movements are smooth and deliberate to minimize extraneous light signals
* The diver keeps looking forward to view the path ahead and navigate.
Model is AWL of Cold Water Kitty.