The faq is a direction translation of
Plus a few pictures.
As far as I can gather,
your friend gains triple experience if you're in the same party as them AND near them when they're questing. I'm unsure if this applies to level 80s helping level 10s level up though! Only the recruiter gets the rocket (
), and the bonus is that the recruited player can grant his recruiter levels (up to 50 levels or something like that).