An apparatus and methods for applying an inner coating to a wellbore screen are described. The apparatus comprises a support for the wellbore screen, an elongate injector for injecting coating material into the inner bore of the wellbore screen, and a driver for positioning the elongate injector into the inner bore and moving the elongate injector through the inner bore to introduce coating material to the inner bore. The elongate injector has a supported end, a distal end, and a coating material delivery line extending through the elongate injector from a coating material supply to a port at the distal end.