BLENDING BASE AND COATS

Take a new V-ray Blend Material. Put the metal material as the base. Add a coat of stainless steel, use the scratches as your blend alpha. Then add the light material as the second coat and, this time, use a desaturated version of the diffuse map you used for texturing the light to use as a blend alpha, and you’ve got your materials! Apply it to the model and render.