Actually, shakes, Spar means soft. Spar finishes are designed for outdoor/marine use and made so they can move as the wood expands and contracts. They seal against moisture very well, but are susceptible to target burn. Thin coats will help to minimize this. Varathane is a good brand, altho I'm not sure how well it will bond with the polycrylic base coats. If you wipe the spar on it should work well straight, but you will want to thin it if you dip. Good luck and keep us posted on how it works.