Yeah, a "heavy" carnauba. I never find them to work all *that* well at this, but having a glaze under the wax will help a lot. In fact, that's what I use on cars that can't stand any more polishing- glaze + heavy carnauba.
The "heavy" waxes include Meg's #16 (and to a lesser extent their #26), Collinite (especially IMO their pastes), and One Grand's Blitz (don't get this on black trim). I hear Meguiar's NXT does some hiding too but I've never gotten around to trying mine.