I use Epifane Varnishes for outdoor clear film work. The Rapid Coat will do a decent job if you want faster results and the ability to add several coats on a warm to hot day[ faster drying than their traditional High Gloss varnish]. I almost never sand between coats with this product due to its thinner nature, and Epifanes states it's not needed either , so it's a win-win.... ;D
If you want Piano Depth type finish and possible more UV protection built-in, then multiple coats of their High Gloss that you can buff the sheen level down to what you want instead of using a flatter varnish. Allow 1 coat a day, with lower outside temps dictating how soon that next coat could be applied. Once I know that the previous coat is dry enough, I lightly buff the High Gloss between coats with 400-600 grit Abranet Abrasive, and vacuum off the finish to get rid of the dust/finish left behind. I tend to use either a Mirka hand held, or Festool Hand held sanding block with the vacuum attachment fittings to keep corns/crud from building up on the surface of the Mirka Abranet while buffing/sanding between finishes. Follow up with a quick wipe of Denatured Alcohol on a rag, and you're ready for the next coat
Last thought. Sikkens Cetol Clear, which is the clear finish that Sikkens recommends people putting over their tinted/colored Cetol finishes for more protection, and few people ever do... [embarassed]
