Joe, I do NOT recommend Mod Podge. I used it on Endgame, and I am disappointed. It has a super adhesive quality, in my opinion better than Balsarite but it has some negatives that I was not expecting. It has bubbled up in several places under the monokote and given the appearance of sharkskin. It may be that it needed to dry longer, or I waited too long. Don't know. I put on two coats a day apart and sanded glass smooth before applying the Monokote. Crist is the one you need get with. His planes look first class. I think he puts it directly on the raw balsa.
I have also used Poly Crylic. It helped fill the grain but not much on the adhesion. My best results on wings have been raw balsa, lots of heat with a gun and rubbing with a cotton cloth while it is still too hot to touch. Good luck, hope to see you at the field soon!
Ken