There's always time to direct models ...
After visiting the event for a few days there, I noticed that there're always models with no one shooting them. In fact, there's no one testing the cars they're posing with. That's a good time to get your "special" shots

, quite a good way to practice for a "Car Theme" shoot too.
For your points.
1. Some of them are models actually. Not all, but quite a number of them. I've seen them and shot some before.
2. Its not really easy to grab a friend and shoot him/her. Like I said, quite a number of the showgirls are models, so its easier for them to face your lens than friends. $10 for a wholeday of practice is cheap, compared to going for group shoot sessions. And who says CLS cannot be done during an event ;p.