I defretted my bass last night, and the wood filler I bought is way to thick and coarse. 1. Does normal wood glue(white one) mixed with sawdust produce a good filler? 2. Do numerous coats of polyurethane wood finish (with light sanding in between) cover up minor nuances on the fretboard? Or do I have to sand it silky smooth? P.s. I´m also thinking about sanding my bass itself. It´s red and I´m more of a wood-man. What do builders use to seal up the wood? Wax?