Copper "grease" is not designated, designed or made as a lubricant . It's intended use is as an anti seize compound. Copper is not a good lubricant or bearing material. Ordinary "LM" spec grease is entirely suitable. The small sachets of copper anti-seize supplied with brake pads are provided for application to the brake pads to prevent them from seizing ( or squealing ) to the brake pistons or calipers surfaces. It's essential that the caliper guide pins should be correctly lubricated to ensure that the calipers are free to float on the pins. I once had some non VW " reconditioned calipers" (supplied by a well known car spares Co.) which had the OEM hard chrome finish pins replaced with Zinc plated pins . Needless to say the calipers partially seized ( with brake overheating) despite the application of LM grease. Zinc is not a good bearing material. The OEM hard chrome smooth finish pins are made to provide a low friction surface. Only a small amount of grease should be applied to these pins.