I may be able to tell you a little bit. We tried to get this organized in my previous driving club, but noone could find enough trail, and we got bored on the road really fast.
Do you have a specific question?
As an overview, they are usually run like competitive trail, with penalties for all sorts of things. We did a staggered start, so every entry had to be recorded, and I think we figured an ideal drive time, and the closest person got recognized. It took quite a few volunteers.
The Midwest club sent us A LOT of info on the way they do their drives, so you may try them.