There could be two couches for each set of winning and losing guests. For the winning guests, maybe there could be clips of Goofy living in his newly-decorated house, while mentioning nothing toward the losing team. Then, there could be a moment of Goofy slipping and colliding with a giant case of Thinner cans, thus eliminating the newly-painted room and resetting the entire house.
I could have something similar to the Midway Mania vehicles, except for being in a constantly spinning state until stopping at a game, this would be much more like a typical dark ride at a constant, non-stop motion. I mean, they wouldn't be the EXACT same designs with that Victorian-style bench seating, but back-to-back seating. Maybe like two couches moving together, similar to the cabs of the Roger Rabbit ride. As for the paint cannons, we can avoid the same design as Mania's cannons. To give the illusion of splatting paint, we could have air blast out with each hit. They will look like the same cannons as in the Tokyo attraction.
For a scoring system, how about some kind of meter that lets you know how much you've gotten painted up? The more you paint, the higher the percentage. You also don't know how much your fellow riders alongside you are getting since they are in a different couch, so it becomes more of a surprise when you lose and they win or vice-versa.