I did a v. light sand after the first coat because I wasn't happy with those dimples, but I don't think it was necessary and in hindsight I could have left it and just done the next coat.  I didn't sand between the other coats as I hadn't seen any significant imperfections or fish eyes etc that I thought needed sanding out, so decided it was better to leave it rather than create any more work or chances to screw it up.