Everyone has sanded through the epoxy at one time or another. If you're talking about a little area like a square inch or so, you can just go to varnish.

On my last boat (a stripper) I brushed on the second and last coat of epoxy very carefully so it was almost like a varnish job other than a few dust spots. Then I hand sand with 350 grit wet sandpaper with a foam block. this makes it pretty hard to take any material off other than prepairing the surface for the varnish.