At VOI 6 in St. Louis, they had two possibilities: A car wash service at the parking garage (not endorsed by Dodge, just a company that did it there normally), and a "wash center" at the track. This one was pretty slick, as they had most of the cleaning supplies provided free of charge. No hi-pressure wand, just a hose with decent pressure and a spray nozzle. But they had all the wash mits, soaps, etc., generally provided by vendors. While I only used it once, it was convenient. Having a black car and successfully trying to weasel my way into the front row of the group photo, I wanted it to be relatively clean.
You will see a LOT of people out there with dusters, Zaino/Meguiar sprays, and towels to do minor touch up. Pretty ineffective if it rains, but generally a good solution otherwise. I plan to bring a couple towels and some Zaino spray to keep it relatively clean. Figure 15 minutes tops, with plenty of beer time left over!
Chris