NEO,
I put on 4 coats sanding lightly in between. After the first coat I sand just enough to knock of dust specks and fuzz. After the second coat I sand a little more aggresively. The overlaps of the glass almost dissappear. I'm using 3M 320 grit wet or dry sandpaper and dry sanding. 4 coats of this stuff fills the glass about equivalent to 2 coats of epoxy but it feels much lighter after it dries. I also found that it's better to wait a day for the final sanding because the poly "sets up" harder and sands better.
Jim