If time was short I'd buy two cheep jet wash programs, the ones without the horrid foaming bush. I'd put the first token in and blast all the large dirt particles off then quickly with a clean wash mitt go over the panels whilst still wet to loosen the hard to remove traffic film, the one that jet washing alone can't quite shift. Then quickly before everything starts to dry and attach itself back on to the paint get the next token in and blast over the car to remove the remaining small dirt still held in solution on the surface. If your car has a healthy layer of wax/sealant the method is a piece of cake. If you work fast enough I find there's enough time to get sills and arches cracked at the same time.
I only use this method as a last resort, generally if away from home and the car is minging. At home it's the buckets, mits, wheel bushes and pressure wash regime 8)
