If your doing car lots then a orbiotal woulkd be the choice for me. They are for the most part looking to get the car shinny and that's about it. I would also look for a wax that has fillers so that you can mask the swrils. With the amount of cars you are going to do you are going to be busy
I'd go for the speed of a rotary. You could turn out cars pretty fast with one of those and your audience is captive. Would be a pretty good learning experience too.
$119 plus shipping from www.coastaltool.com - Porter-Cable 7424 Polisher & Sander 6" Random Orbit with Bonus Kit.
Standard Equipment
7424 Polisher & Sander
with 5" Counter-Weight
6" Foam Polishing Pad #54745
Wrench
Operating Manual
Bonus kit includes:
The hook & loop backing pad and 6" counterweight we decided to include it with the 7424 Polisher at no cost in this special package.
6" Hook & Loop Contour Pad #18002
6" Counterweight