Either way works- - - -I prefer to do it before I start up to minimize any possibility of creating unwanted voltage spikes in the rest of the system. Once it's polarized, grounding the field wire either at the generator or the regulator should put it into full output as long as the ground is connected. It basically bypasses the voltage regulator.
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!