: Hey everyone, I've got my 14' great auk just about ready for
: varninshing. I've got a lot of imperfections in the epoxy
: (fiberglass strings, bumps/dips etc.) I plan on doing a light
: sanding and then doing a skim coat or two.

Spend another day or two fixing the glass before you varnish. Strings and bumps you sand off. If that cuts into the glass cloth a little just cover with a little epoxy. Dips you fill with a patch or two of glass cloth wetted out in a teaspoon of mixed epoxy. When the patches are hard sand them flush and start your varnishing.

First coat of varnish over fiberglass can take a week or more to harden. Thinning it with 10 to 20 percent thinner seems to work for most people.

Read the label on the varnish to see what the preferred thinner is. I'd hate to tell you to use paint thinner if you have a water-based urethane.

: Would a ROS with 120
: grit be too aggressive for this step?

Probably just the thing. Use a light touch over most of the boat and spend more time on the bumps and strings.

You'll want a finer grit when you sand the varnish.
If you don't flatten out the bumps before varnishing then any varnish you put over a high spot is removed with the first touch of sandpaper, which is a waste.

Whatever areas you miss now you can repair in the fall when you patch all the accumulated dings before storing the boat for winter.

PGJ