Use a coin-operated car wash with the following steps.
Take anything that needs to be washed or kept dry out of the car. If washing floor mats, get them ready before inserting coins in the slot.
When spraying the car, start with presoak, followed by the soap cycle and then the rinse cycle, remembering to spray the tires and inner fender wells to remove salt and road dirt.
If desired, finish with the wax cycle and use a chamois or soft, clean towel to dry off the car.