I only hand wash and I've had the front grille done for about 3 weeks, so couldn't say. Other people have said it holds up to a pressure washer. Not sure about the harsher detergents in the touchless washes tho.
Don't sand! A, you dont need to, and B, that takes away one of the biggest advantages of Pdip--it's removable, if you ever wanted to go back to your original finish. Just spray a light coat on the first pass (look at my first bowtie pic), 50% transparency, and then you can build the rest of the coats on that