It sounds like the liquid sheet I've used from wowplanes.com.. It works pretty good.. Let it dry and sand with 220 then prime.. Not sure on what it would add for weight though.. I used it on the AR-6 plug so I didn't care about the weight.. If you want I meet you next time you're in MSP and give some to try..
I have used it and it worked well, I liked it because it is white. After several years rust developed in the can!! Now I use poly prime from PCL ( pacific coast lacquer ) it's the best I have found so far.