in all my 50 years of modeling, the fastest glue I have found is 3M's 77 spray adhesive. You spray each piece { balsa and foam} let them air out for about 10 minutes, then stick them together. Make darned sure you have them exactly where you want them, because once they make contact, they are not coming back apart! A lot of peop;e on here use Gorilla glue, I guess it works good ( I" ve never used it ) but sheeting my wings and waiting 24 hours for it to dry is not my idea of building!
With the 3M i'm sanding and cutting out the control surfaces with in a half hours time.
Just my idea of building!
Good Luck Art