I use this model pressure washer:
http://www.homedepot.com/h_d1/N-5yc1...1#.UKO_YG_LSOA
I use the 40* nozzle and it works very well. I also picked up a foam gun they had on clearance for $29. 2oz of soap mixed with water and it produces loads of foam. I usually do a light prerinse and then use the foam gun to let the foam dwell on the paint and loosen up all the dirt. I use two bucket method to actually wash the car.
If you do use a pressure washer that has multiple tips, be sure to always spray torwards the grass/yard the first time you pull the trigger after changing nozzles...much better than replacing a windshield
Great tool to have around, makes cleaning the siding on the house so much easier.