Here is a trick with white glue, it works better than balsarite. Mix up some Elmers or similiar with water till it has the consistancy of milk, then spread a coat on the wood you are covering, let dry, sand, add a bit more glue to the mix, and apply another coat. Do this till there is no rough fuzz, but do not try to seal it as with sanding sealer. Now when you use a film covering such as moneykote or ultragoodcote it will stick to the glue. However, the white glue does not actually melt, but the heat does cause the outer molecules to cling to the film adhesive, I do not understand why. This only works one time as the heat changes the molecular structure of the white glue. The good part is unlike balsarite it will not come loose near a hot muffler or in the hot sun, though the film adhesive may.

I have used this trick where film did not want to stick to fiberglass, even after sanding the glass.