i started by doing it accidentally, but then i found the pattern of when it occurred, and it was always when i yawned or rolled my tongue back.
so, i can do it on command now, and when it refuses to spray, all i have to do is fake yawn, and it somehow makes the saliva accumulate under my tongue. then when i try to roll my tongue back and do it, it works like a charm.
Caution: dont attempt this in public for long periods of time, you will look like a tweaker if ur constantly yawning over and over and then rolling ur tongue back while opening your mouth.
P.S. it works the best once you've just had something to eat or drink...cheeseburgers work great.