If someone eggs a car, it's important to act quickly. Removing the egg as soon as possible limits the damage that acidic egg whites do to the clear coat and paint. Washing off the bulk of the mess, rehydrating it first if necessary, then getting a professional to check the car's finish is the best way to reduce the damage caused./
If you discover the egg while it's still wet, use a pressurized water hose to wash it off the surface. Prevent scratches from any pieces of eggshell by avoiding use of a sponge or rag at this point. If the egg has dried, set up a lawn sprinkler to spray on the car and rehydrate the egg. Once it's wet again, spray using a hose pressure nozzle to remove the egg. Use a detergent designed for washing cars, or a mild dishwashing detergent solution, to sponge the area and remove any remaining traces of egg. Rinse with clear water.
Professional detailers are often able to remove the damage from an egg without having to repaint the vehicle. Be sure to point out the area of concern when dropping the vehicle at the shop.
Comprehensive policies should cover any damage from vandalism. Notify the insurance carrier even if the egg appears to be completely removed in case the effects of the egg become more noticeable over time and the car needs to be repainted.