For wood hulls is it a good idea to use spar varnish and seal the entire hull including the bottom before fiberglassing the bottom?
Same here. Although because I seal with the same resin I 'glass with, I don't have a conflict. It's also handy because when I'm epoxying something on ship A and wind up with a little extra epoxy, I can use it to seal a little more of ship B, minimizing waste.
okay thanks. Is there an added benefit to sealing with epoxy rather then the varnish or is just easier and cheaper to use what you already have?
I think that the epoxy holds up better over time, but I've done boats in spar varnish and they've lasted years. YMMV.