Convenient and fast (for a cheap wash)! I do the $5 drive through, then park it and use the vacuum & compressed air. They also give you a little blue interior cloth to wipe off the dust inside the car. It's convenient because you can stay busy doing that while coasting through the suds. I see some people bring shammys or towels with them for drying purposes. Seems a little unnecessary to me since they provide the compressed air. If you are quick, and fan off the water droplets the drier missed, you can get a very clean looking car for minimal effort.