While you basically can't "smooth" out CSM, if you use a bubble roller, it does help some to lay flat. But CSM was never made to be a subsurface for a smooth finish. But then neither was 1708 either. The are merely fiberglass mats and weaves to assist in building or rebuilding structure. You have to sand and fair them for a smooth surface if you have plans to use them for smooth surfaces. When boat builders use them, they are applying Gel Coat on their molds first, followed up with either a chopper gun fiber shoot, or hand laid woven mats.That is why those procedures come out flat and shiny. JMHO