Minch, for sanding and fairing, IMHO, you should always finish with CSM. The fibers in the Fabric/Cloth won't sand very well. The CSM kinda dissolves in the resin and will sand nicely so I always put down a couple of layers of CSM over the Fabric. I even try to grind/sand it a bit low and then fill it with some fairing material to ensure it all sands and fairs easily.