You can remove plastic covering on the seats, fenders, and hood, plus vaccum the interior, clean the windows, and wash the car in 30 minutes?! $54 an hour to do this to two cars? Jeez, I'm in the wrong business!
What product are you using to remove the cosmoline before you wash it? What products are you using to wash the car and dress the tires?
If you are already doing this for a dealer, you have to be getting your produts somewhere since you are able to calculate your cost per car. Why don't you just get a spray wax from the place where you get your other supplies? What spray products do they have?
To answer your question, any decent spray wax can go on windows, plastic, trim, etc...
Sparkle Auto sells Eagle One Wax As U Dry for $17.99 a gallon. I'd use that since you apply it while drying the car. Seems to be the cheapest of all the recommendations and a more effective use of your time. You mentioned you used a chamois. You'll need a microfiber drying towel instead.