OK -- I know this goes against almost every single piece of advice, but...
You can't shave your pubes like you shave your face. Up top, you're going for the close shave; and if you were to subject your face to the same crotchal-environment (chaffing, sweat, etc) you subject your junk, you'd be red-faced in no time. And I avoided shaving my pubes completely because the one time I did (in the shower, with girly shaving gel and a good razor) I spend the next week in agony, scratching and twitching at the huge rash of razor burn that ensued.
Then I read what sounded like the stupidest advice... but tried it anyway. And now, I shave as such: Gently, with a dry razor, absolutely no cream, water, moisture of any sort, BEFORE I shower. Yeah, it doesn't get AS close a baby-smooth shave as you'd get using products, etc., but I never, ever have a problem with razor burn. Just make sure you go lightly, and WITH THE GRAIN.