How is static electricity is used in paint sprayers?

The paint is charged with an either a positive or negative charge, and the car part being painted with the opposite charge, the two charges attract and the paint sticks to the car part.This process ensures a uniform layer of paint, since when there is enough negative paint in the car the extra will be repelled by the paint already in the car.
It also ensures that the paint won't fall off, since the electrical attraction between the paint and the car is stronger than if it was just sprayed.