Subu,
saw your foam model of the v22. If things are going fine, then why are you looking for balsa for aerofoil.
Some pointers (even if you don;t need it).
I have used balsa with surgical scalple. Normally, balsa cant be cut easily, but be warned that some cases, you need to apply good amount of pressure. With a sharp knife, do take extreme care so as not to hurt yourself till you get hold of handling the knife and wood.
I had used quickfix adhesive to joining, used to take a long time but its more fun when it takes time
, and I never had problem of sanding.
Building a balsa frame based wing is a lot of fun..... you would need to draw out the ribs and create a template of sorts. Then once every rib is cut, you would need to sand them together. Then when the ribcage is ready, then applying paper and then dope is a lot of fun actually, but time consuming.
If strength of thermocol/foam is you issue, then you might want to strengthen your wings with some spars. I have seen some folks do this as well...
Pankaj