nitrous and 4.6

[ac97gt]

i guess this is a little off topic, on topic, but how exactly does using the nitrous work? do you hit and hold the button as long as you want the juice to come out? if thats the case do some people put in toggle switches that would leave it on until you turn it off? when do you start spraying and how long do you leave it on for? about how many seconds (or minutes) or constant spray can you get off an average bottle at say, 100 shot? just curious, i dont know much about it.