Epoxy is great for sealing grain, but it should not be used as a top coat as it has no UV stabilizers and will eventually cloud up and/or come apart. Many wood boat show queens have a first layer of epoxy, block sanded to smooth and flat, with a few layers of real varnish op top. The epoxy fills the wood grain and provides that super-flat initial film, then the varnish provides the UV protection and silky-smooth top coat.
I was glad to see ramblinrod's recommendation of an acetone treatment after sanding, but I want to elaborate. At the point in your finish prep where you are ready to do an acetone wipe-down you need to understand you are removing
two things with the acetone and rag(s). An obvious thing being removed is the sanding dust. The other is oil.
What people often don't consider is that many boat building woods are naturally oily and trying to apply varnish to oily wood is like trying to varnish a teflon pan... It will peel right off. When putting any finish on wooden boat parts, you want to remove the oils from not only the surface of the wood, but down in the wood too. Displacing the oils with the acetone scrub allows your finish be it epoxy, varnish, cetol, or whatever to dive into the wood rather than just lying on it.
SO...
My recommendation at acetone wipe-down stage is to have a bunch of white rags handy and ready to go. Start with a clean acetone-soaked rag and clean off your part. Throw that rag aside and get another clean one. Soak it and scrub. Do this repeatedly until whichever rag you are working with stays white with no discoloration. Do this in a well-ventilated area please...
Wiping to "clean-rag" stage ensures that you have removed surface oils as well as scrubbed away oils even to some depth in the wood. Then, when it is time to apply that first thinned coat as ramblinrod suggests, the finish will go into the wood. This will give your total finish build a much better mechanical grip to your work piece and will give you a much longer service life.