I use the Balsarite made for film. It helps a great deal. It goes on like water and helps the plastic covering stick well. It also fuel proofs the wood. Balsarite comes in two formulas. one is thick and is used for covering that has not adhesive and the other is an adhesive promoter. I have found it helps to keep wrinkles down on sheeted area.

I quick coat with a foam brush over the airframe and two coats on the firewall and fuel tank area. Takes about 5 minutes to dry.

Dru.