What's with all the thinner?
Thinners are usually used when coating bare wood to get the coating to penetrate and grip the wood better. Coating epoxy or another coating shouldn't require any thinning because no penetration is possible.
And, epoxy is your water barrier. The varnish is used just to pretty things up a bit and to add the necessary UV protection.

: I used Goldspar on my last kayak and it was great stuff. I also have used
: Epiphanes for non-kayak projects with excellent results. Just make sure
: you get the thinner made to go with the product. Don't use off-the-shelf
: thinners. The one for the product will allow proper drying times. I thin
: it 50/50 for the first coat, and then each succeeding coat I use less and
: less thinner until the last coat is only 10 percent thinner.