Yes, you can use it in a pressure washer, the only issue is the relatively small quantity needed to wash a car. If you have a mixture control that will meter the contents of your soap solution, it might work. You only need an ounce or two in a five gallon bucket of water. Use sparingly or you could end up with a driveway full of suds!
This product can be used to clean the entire automotive exterior. It does need to be thoroughly rinse and the windshield should be dried with a clean chamois or soft cloth. In some cases a glass cleaner might be recommended after washing the vehicle.