Probond
Probond is put out by Elmers Glue. The nice thing about it like has been said is that expands and fills the seam of the sheeting so you dont have to glue it together first. As for sanding it sand very easily the nice part about it is it sands about the same as the balsa does thus you dont end up grooving balsa like you would if it were normal white glue, epoxy, or CA
Joe