The epoxy and varnish both have a coloring to them even though they're 'clear'. I'd suggest the varnish be first and then end with the paint. Painter's tape is cheap. Removing the tape while the paint is still drying would keep it from sticking.

Painting in two tone always presents the question of which to do first. In your case, is it going to be the hull or the deck that gets painted LAST.

That was a hint.

If it were my project, I'd would want to complete the presentation side (the varnished deck in your case) of the boat last so that the new finish would not be marred or damaged during painting of the hull.

I suggest you tape and mask off the upper deck to within one eighth inch of the final line where the hull paint ends and the varnish begins. Then carefully place your half inch wide fine line tape overlaping your previous mask and to make that final line. Press it down tightly!

Then remove the fine line tape while the hull paint is wet so that the edge lays down nicely. Depending upon the paint used, temperature, tack free time, this amount of time can vary. If the tape comes off with strings of paint attached, you've waited too long, so try lifting it sooner on the next coat. Of course, you'll be re-taping with fine line for every coat.

When you're ready to varnish, check a small are of the hull paint to make sure it is dry to the point of "tape free" by pressing a small section of your fine line tape onto the newly painted hull and wait 30 minutes to remove it (at room temperature) and see if it leaves a print. If it does, wait longer to back tape for your varnish, using the same technique as you did the hull paint, mask off the painted areas. Do this in a inconspicuous area.

 Varnish two coats and wet sand with 400 when dry. Varnish two more and wet sand with  500 or 600. Final coats can be sprayed for that perfect finish, or brushed using a fresh can applied at the best temperature for flow out.

Depending upon your choice of varnish, you may want to wet sand the final coats with 1000 and buff to a high lustre. 

That was a big help.  Thanks! Looking to start that phase in the next week or so