You don't even need to be a font of knowledge to help new players. Telling them where and when they can unlock their chocobo (one the biggest questions of all times in NN) isn't exactly rocket science.
And even then, you don't even need to reply to questions if you're not sure of yourself or unwilling to, someone else will do it and that's why there isn't just one mentor, they all have their specialties. I know a lot of sprouts turned mentors that just PARTICIPATE into the chat, talk to new players, or run content with them, and that is already invaluable, more than all the ghosts that park in the chat and never say or do anything.