RE: How do you finish your balsa C/L?
On solid surfaces, I've been using rustoleum. Seal the base with a thinned mixture of lightweight spackling and water. Sand smooth and then hit it with Rustoleum sandable primer from the ole rattle can. Sand that smooth and hit it again. A little 200 grit to smooth the rough edges and hit it with whatever solid color Rustoleum you like in whatever pattern you like. It's ready for a second coat in an hour or so, read the can, and ready for taping the next day. 5-7 days after you've sprayed it is fuelproof to around 25%, I haven't had any problems with it and 25% fuel.