All you usually need to do is rev the engine once. Most alternators will "self-excite" once the speed goes a little above idle. You can attach a wire to the terminal you're using to "excite" things from the ignition switch, or if you're not comfortable keeping the voltage on it all the time, use a push button starter switch. I'd recommend keeping the reference voltage on it all the time the key is turned on.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!