Let me add to what MikeBoyd said. I too build with wood glue (Elmer's Carpenter's Glue), and yes you need to wet the sheeting before you apply it. But you don't have to stop at just spraying it. You can totally soak the wood if need. I usually take the sheeting to the bathroom and run it under the faucet of the bathtub to wet it. You'll need to do this more so on harder brittle balsa. When you wet the wood like this make sure that the wood has dried before you remove whatever you used to hold it in place while the glue dried.

Ken