[Heinkel-162]

The air wars of World War I were mainly fought with fabric covered biplanes that were vulnerable to fire due to the flammable properties of the Grade A cotton covering and nitrate dope.The German aircraft designer Hugo Junkers is considered one of the pioneers of metal aircraft, his designs started the move away from fabric covering. The highly flammable mixture of fabric, dope and hydrogen gas was a factor in the demise of the Hindenburg airship.

So there is your coating, Nitrate Dope, it is available for Hobby Aircraft aswell so you could get some their.