A system including at least one means for mechanical processing of surfaces using a blasting agent (5), in particular steel or cast iron beads. An additive (6) for degreasing and cleaning of the surface to be blasted (2) and/or of the blasting agent is provided with the blasting agent (5), and comprising a granular material (6), which exhibits a lower breaking strength under the mechanical stresses that the blasting agent (5) is subject to during the blasting procedure than the at least one means for mechanical processing of the surfaces themselves. As the granular material (6) breaks down, additional additive (6) is added into the blasting agent (5) such that the proportion of the additive (6) in the blasting agent mixture blend (5) remains largely generally constant even at a prolonged operation of the device.