I dont see why not. it may not finish as well as oem clear but some body/custom shop clears will harden more then oem. i might have to do some testing and reclear an old scrap panel and see how it comes out.
250k unless i did the math wrong
100$ x 8 cars a day=800$ a day
800$ x 6 days a week= 4800$
4800$ x 52 weeks in a year=249,600
it will be less then that since he's doing it 6 days not the full 7.