They use dawn soap to clear crude oil spills off animals. Only use it on a car before you plan to do some serious waxing (clay, polish, glaze, wax, etc).

I use Meguair's products myself. Great quality, not super expensive, can be found anywhere. Can't go wrong with Gold class, but have been using the new ultimate line on the mustang.

Also look into the two bucket method for washing. It helps with eliminating any grit and dirt from causing swirl marks.