Dan, things to bring. Hide a cooler inside your car for some tiny drinks (no alcohol per rules). Bring a sweater, it'll get cold when daylight is gone and the cars are driving by you.

As for the car wash. We didn't hit any local car washes last year. All we could do was meet up at the hotel and just try and clean the car as best as we could. You could bring some water (in some milk jugs), bucket, soap and whatever you use. You probably just need to clean off the side mirrors, and the front fascia. You can use windex and paper towels to wipe off the windshield.

Best advise is to wash the car up at your place, drive down early in the morning (turn off fog lights to not attract bugs!!) and hope for the best that you dont have too much cleaning to do.