Apparatus for electrostatically applying a coating of a particle material to a substrate surface to which a settable adhesive has been applied, including a container for the particle material which can pass gravitationally to a power-driven agitating and metering device and through an electrostatically chargeable electrode from which the charged particle material can then pass downwardly through a main discharge opening to the substrate surface, or said main discharge opening can be closed and the charged particle material can then be fed by the agitating and metering device to an air operated injector device from which the particle material can be delivered through a flexible pipe to a portable handle device to which different subsidiary discharge heads can be applied and electrostatically charged electrodes are positioned at or adjacent subsidiary discharge head openings to again charge or boost the charge applied to the particle material prior to discharge towards the substrate surface.