A very light sanding will remove any fuzz and give you a nice fresh surface for the epoxy to bond with. It's almost always easier to do that before things are assembled.

Some people also pre-coat some things with epoxy, especially parts that will not need to be bent into curved shapes after the epoxy has cured. If you decide to do that, it's not a bad idea to keep the epoxy off any areas that will later be bonded to other parts in the boat.

Old Yeller 

I can only support Yellers words. Do really sand everything very smooth, no scratches should be

seen anymore. We have made this mistake of being not carefull enough. Some scratches became

visible with the first layer of epoxy and now are burried forever.

Reinhard