[calgarychef]

Funny I'm just refurbishing a big fiberglass laker canoe. Going to Calgary industrial plastics is a good idea. If you just want to smooth the bottom nicely a good sanding with a good sander and proper sandpaper will be a good start. Then you can use "fairing putty to smooth out any deep gouges. Then some good paint and you're away. West systems makes good marine epoxy paint and it's expensive.

You also might have the option of adding a sheet of UHMW (ultra high molecular weight) plastic to the bottom. That stuff slides over rocks nicely I've heard. I haven't used it though so you'll have to research it yourself. It sounds like a great alternative though and if it wears through you can replace it.