As a sealer and to give a good finish then epoxy resin is one of the best. A good idea is to thin the first coat to help it soak into the wood and harden the surface. Adding some microballoons will help when it comes to sanding and will give a smooth surface without needing several coats, sanding in between to fill scratches from sanding. It doesn't need a lot of microballoons as you only need enough to slightly thicken the epoxy, you are not using it as a filler for large holes.
Jim