You'll definitely want to trim the pubic hair, but not shave it. If the hair is too short or too long, the wax won't adequately grip and pull the root out. Consult your esthetician, s/he can give you an idea of about how long the hair should ideally be for a optimum wax.

Consider taking some ibuprofen just before your appointment to help reduce inflammation and pain. Also, make sure you have a loofah on hand...starting a few days after the wax, you'll want to exfoliate any waxed skin to prevent ingrown hair.

I've received Brazilian waxes, but the people willing to perform them for male clients are few and far between (at least where I live). I'm also now wearing a chastity device full-time, so doing a quick shave in the shower is my MO now.

Good luck and let us know how it goes.