Get the car in the shade and wash small sections with a terry cloth rag and Comet. Yah, the bathroon cleansing powder. Use the new formula that doesn't scratch. It's super mild, yet cuts through dirt and age-old, stuck on grime. Work in circular patterns and use even presure. It is especially effective on white and light colored cars, but works great on dark colors too. Rinse well, and don't do it in the sun. Also, only sprinkle it on the cloth not the car.

After you've done the entire car (glass, chrome and rubber) and rinsed well; wash the whole car with a bucket of warm water and a half a cup of kerosene. Buff to a brilliant shinewith a terry cloth towel. It will also help combat rust formation in the nooks and crannies.
For you non-believers, try it on an inconspicus area and you too will become a believer. It's all I use on all my vehicles.