As written in the manual I used Auto Body Filler to get a smooth retainer surface. This Auto Body Filler really works great. After 3 layers of this filler and some time of sanding, it ended up in a clean, nice and smooth surface. It works really quick. After 30 mins of drying you can sand the filler. I have never used such a filler before and I am really impressed of this polyester resin.
