Originally Posted by lr172
I would love to do this in a trainer's RV, but figure that may be unrealistic. I can either rent the instructors aircraft ...
Not just unrealistic but in general not legal. An RV owner offering his aircraft for rent for transition training will have a waiver ("LODA") allowing him to do this - but the waiver is generally good only for bona fide transition training, not "knocking the rust off".
Plan to rent a normally certified airplane to get current (including a Flight Review). Then go to transition training.