An apparatus and methods for applying an outer coating to a wellbore screen are described. The apparatus comprises a support for the wellbore screen, an injector for injecting coating material on to the outer surface of the wellbore screen, and a mechanism for positioning and moving the screen relative to the injector and/or moving the injector axially relative to the screen to introduce coating material to the outer surface of the screen. The apparatus further comprises rollers for distributing the coating material over the outer surface of the screen. The elongate injector has a coating material delivery line extending through the injector from a coating material supply to an open tip.