You might try wet/dry sand paper (use it wet). Start with fairly coarse grit and work towards a finer grit. Kiln wash is typically the separator that is used, since fiber paper will leave significant texture (and ThinFire/Papyros may “move” and become embedded).
Steve Immerman has a pot melt tutorial on his web site: http://www.clearwaterglass.com/Tutorials/AperturePour.html
Jester’s Baubles Fused Glass Designs