I like to work with cardboard because it is very versatile and usually free. Im nearing completion of a new costume and could use a little advice. The construction is solid but I was wondering if anyone had tips of cardboard finishing and paint prep. I mainly want to hide the corrugation of the cardboard for a smooth surface. I've used primer and paint before but although the paint works it still generally looks like cardboard. I've been researching online and have pieced together a few ideas. First: I have been using wood filler to fill holes and strengthen light pieces. This works but the wood filler doesn't spread so great over large surfaces. Perhaps its the type im using. Second: I've read a lot of good stuff on spray shellac. Everything I read said that should be on the cardboard before anything else. Then use your fillers and sand on top off it. Third: Filling in corrugation ruts with with joint compound or something called paper clay then primer then paint. Fourth: Bondo-I really would like to avoid this one as I cold see it getting costly. Any tips, insight or even tutorial links would be much appreciated. Thanks in advance.