Mike,
You are correct. They came out with the spraycan about 2 years ago. It really makes this a very convenient and easy to use product. I had the same issue the first time I tried it. At the time (~3 ish years ago) I tried the 4oz sample and tried to seal with plastic wrap, didn't work. I have had the spraycan on the shelf for over a year and used it a couple times. I have been working with the Liquitex water based 100% acrylic rattle cans and then top coat with the KBS, works great and just about the same weight as dope. Also been reading about what the scale guys are doing with latex paint. Seems you can thin it out for low pressure spaying and it is also pretty light (what they say is less than epoxy or acrylic enamel (like Rustoleum), overcoat with KBS. Supposedly the important thing is to get latex that is 100% acrylic resin (the most expensive). The big advantage is it can be tinted any color you bring a chip for. I did a quick compatibility test with just some cheap latex I had in the house to overcoat with the KBS spray, worked just fine. Might try it on something small. Would be great to be able to get different colors that aren't $75 a pint.
Best, DennisT