Put me down as another vote for KlassKote. I used to finish all my planes with K&B, and even though it was messy, and smelled pretty bad, it wasn't hard to get a nice finish, and was incredibly durable. I have a few partial cans of color and only a little bit of catalyst and thinner. I ran out a long time ago with enough to paint a whole plane. I've tried all the various alternatives, including latex, Nelson System Three, several brands of automotive, several of the spray cans (never again!!!), and nothing was close to good old K&B. I was really excited to see KlassKote. I talked to them at Toledo (really nice people!), and used it on my last project, a quarter scale Tiger Moth. I don't think it flashes dry to the touch quite as quickly as K&B, but everything else is as advertised, and exactly like I remember K&B. Sprays easily, flows out great, covers well, drys rock hard, is completely fuel proof, etc. I switched to HVLP, so I use much less than I used to with a pressure feed touch-up gun, plus it's a snap to clean up. It's not cheap, but certainly cheaper than automotive, and easier to use as far as I'm concerned. With the HVLP, I only need a few ounces for pretty large paint areas, so the cost isn't that bad. I understand it's 100% compatible with K&B, so you should be able to mix and match with what K&B you have, although I don't have enough K&B left to bother.

BTW, I've heard nothing good about the K&B replacement Ultrapoxy, and it's not compatible with the old stuff. A friend in my former club (who's a good painter) tried to paint his pylon racer with it, and it wasn't nice. He sanded it all off and went with automotive.