Nancy, re: thinning the varnish, Rebecca Whittman, one of the true gurus on boat varnishing, writes: "Don't play chemist * * * read the label for recommnded thinners. Most good varnish companies package as companion products to their varnishes a drying-retardant to aid brushing and an accelerating thinner for application in cold climates and for spraying. If you add whatever you have lying around the shop as a thinner, you run the very real risk of ruining the varnish. Companion thinners may cost a little more, but they are worth every cent when they eliminate the guesswork attendant to using solvents."

For an epoxied boat, you won't need to thin unless the varnish itself has thickened up (usually happens only after its been opened and reclosed and has sat around awhile). The instructions for thinning the first few coats usually assume you are going on to bare wood and you do the thinning for the first few coats so that they absorb better into the wood. Not an issue when you've epoxied first.

If you do thin, don't "stir" in thinner. It will add bubbles. Add the thinner to the varnish through a strainer (paper type, available for a few cents each at almost any good paint store) and then gently "rock" the varnish container to swirl the varnish and thinnner around and around, mixing them in fairly short order and without bubbles.

Good luck!