Baby shampoo can be used to wash a car if done correctly. Use a diluted blend to take bird droppings off the car as soon as possible even if there is not enough time to wash the rest of the car right away. Baby shampoo is gentle and breaks up the bird poop efficiently. It can be easily wiped away without chipping the paint. Be sure not to let the shampoo stay on too long or be exposed to too much sunlight, which may cause the paint color to fade.