Don't let your dealer wash your car. They aren't doing you a favor. They are damaging it. Wash your own using the correct methods and cleaning tools.
99.9% of the time, the person who is washing your car is the lowest paid person on the dealership's staff. I ditto what @grendels_m3
said, that unless the washer is using correct methods and has the right equipment, they can in just one wash, scratch the crap out of your paint.
When I got my new '15 Z06, I had it in writing that the car was not to be washed by anyone but me. So as I arrive with my two 5-gallon buckets, each with a grit guard, two new microfiber wash mitts (in case I drop one onto the ground), three new, extra-large waffle-weave MF drying clothes, etc, and as I go to start to hand wash in their covered bay (it is an outside bay and it is 33 degrees and windy), I notice that ahead of me inside the bay is a farm truck with inches of mud on it and on the bay floor, with a very young man taking a pole-mounted wash mitt, dipping it into a dirty bucket with soap suds, washing the truck. I wait. He pulls the truck out and comes over and, with dirty clothes on, wants to drive my car into the bay. Not happening, and before I pull it into the bay, I hose down/clean the entire bay's floor. The young wants to help, so I asked him to please take my two clean buckets into the service building and fill them both with totally hot water. When he returns, he again reaches for his dirty pole mitt. I get between him and my car and we have an "educational" conversation. As I just handed him a $5 bill, I explain exactly how this is going to work, i.e., he will mostly sit on the old stool in the corner, watch me properly wash my car with my equipment, and all he can do is ask questions. Since I gave him the largest tip in his probably 16 year old life, he truly did listen while I washed my car, explaining each and every step, and reason, why and how to properly wash a car. When he gets his first car, I hope he will wash it properly.
I do not ever take that car, nor my '17 WRX DD, to a top of the line car wash -- for what if that very muddy farm truck was the last vehicle through it. Nor will our Mazda 3 go to a car wash, nor similarly ever be dealer-washed.
BTW, this pic of my car inside the wash bay, before its rear spoiler, side skirts and more were attached to the car as part of the PDI.