As I notice no one else has replied to this, I'll give it a shot.  If you search the forum, you'll probably find more posts on this subject.

The short answer to your question is don't use paint under the epoxy.  The epoxy and paint won't stick well enough to create the watertight bond and strength of the epoxy on bare wood.

A slightly longer answer involves either fabric or rice paper.  Again, there are multiple posts on the forums about either of these methods.  Fabric and rice paper allow the epoxy to fully encapsulate them, and thus don't weaken the bond between the epoxy and the wood.  The epoxy flows through the pores of the paper, or the weave of the fabric to create a strong bond.  These applications go underneath the fiberglass if the area you're covering is glassed, or just on the wood if there will only be epoxy.

If you really want to use paint, paint can be applied *after* the epoxy.  Paint will protect against UV, so you don't need to varnish over it, but if you'd like a bit of protection for the design, the varnish can be applied over paint.  Just be aware that most varnishes will impart a slight tint.

Hope this helps,

-Matt

   Thanks Matt, you just save me from making a terrible mistake!  I'm so glad I asked!  I'll pain on the epoxy then varnish over it.  Much oblided!