Pretty self-explanatory from the title; Do a nosebug into the finish, but you flip in the opposite direction (backflip) so the airbrake won't work, and the more optimal is a counter-steer. As an intermediate map builder, I know I can do better with the bugslides, nosebugs, uberbugs, rally-ubers, etc.
The nosebug part at the end is tougher than it looks, so all I'm saying is good luck, because I tried and failed at the nosebug.