Your job of smoothing the edges would be made easier by using some fairing
compound. It is like marine bondo ( autobody filler) in its function.
You can make the fairing compound yourself with a mixture of resin,
microballons and cabo-sil. Or you can buy it premixed. Maybe that would be a
good idea? Look on the various online stores that sell FRP boatbuilding
supplies and get some. It should be available with polyester resin or epoxy
resin. To sand it smooth, get some 2x2 lumber and make a few sanding blocks
about 10-12" long, glue or staple some 36 grit paper for roughing it out
then some with 80 grit. Then apply some elbow grease.

--
Ron White
Boat building web address is
www.concentric.net/~knotreel