I would suggest stripping the plane down, otherwise the added paint is going to add a lot of weight. When stripping it down be VERY CAREFUL is using a stripper as many of them will attack/play havoc with the fiberglass.

Once it is stripped down you can either apply glass cloth or silkspan to the sheeted areas and paint in the usual manner.

If the wood is not covered it will eventually crack the paint due to moisture fluctuations in the air.