: I epoxy seal coated my deck for stability prior to taking off the
: frames so I could glass the hull. The hull is glassed and now
: I'm ready to go back and glass the deck. How hard do I need to
: sand that seal coat on the deck to get the glass wetout to
: adhere well? Do I just need a light sanding with 120 grit or so?

This from Rob Mack's Laughing Loon site (http://www.laughingloon.com/epoxy.html) describes it well:

"Coating Bare Wood (Seal Coat) Before Glass Lay-up
Roll on a single coat of resin using all the procedures outlined above for maintaining thin epoxy. The wood will absorb the resin at different rates in different areas. DO NOT apply more resin to a spot that looks dry. If you try to do this you will build up extra resin in adjacent areas which could effect the wood color making it look blotchy and creating high bumps of unabsorbed resin. The single coat of resin will do the trick. Do not sand the surface if possible. I use System Three Resins which allow up to 72 hours before sanding is needed. Check the information provided with your epoxy or contact their tech support for when sanding is required. If you must sand, sand only lightly with 120 grit to create a tooth for adhesion, don't sand off the seal coat!"

If you've left it loing enough to harden up and develop any blush, you'll have to remove that (water and a nylon scrub pad is sufficient), but if you're within the cure time, no sanding or at most light scuffing (as Rob describes, or even just 80 grit) will do.