Setting for two years, it should be "Hand sanded" with 150-240 for proper adhesion for the next coat of epoxy. (my preferred choice is 180)
Do not use a DA but just a fast sand job by hand.
It would also be very worth your while to spray two more coats instead of just one for maximum adhesion.
Also note, when done sanding and after washing with wax and grease remover, let the car set for an hour or two before applying the epoxy because of the age.