It depends on what you're going to do. I usually only use one coat or epoxy to seal the MDF and move on from there with a primer (and then a 2-part topcoat if I'm really fussing - but usually primer is fine) and use that to build as glossy a surface as is needed.  Make sure primers are chemically compatible!  

You could also use you epoxy as a primer and add another coat and sand that to 600-800 grit (or whatever you feel like) and then apply release.  I haven't tested it but my guess is that a mold primer/sealer like Easy Composites S120 (or Chemlease 2737 or Marbocote N1000) followed by a semi-permanent release system would work fine.  The surface can't be porous though or it will stick.