I use my pressure washer with the Ryobi Foamer attachment.
Ryobi Pressure Washer Foam BlasterI use the Blue Coral Foam Car Wash not the Ryobi soap because it is to expensive.
Blue Coral High Foam Car Wash Concentrate I spray the soap on let it sit for a few minutes or so and then go over it with a long handled car wash brush. I can get it really clean in less than an hour. If I have any black streaks I spray them first with the Awesome cleaner and let it sit for awhile and then wash with the foaming soap. I rinse with the pressure washer using the foam attachment as it is low pressure and won't damage the finish. The attachment has a lever that controls if you want soap or just plain water.
I can actually do this in the storage yard using my generator and onboard water tank. My pressure washer is electric. By doing this frequently I don't have many issues with black streaks or bugs etc..
Dave