I don't know how to get epoxy off (except sanding), but Acetone works great for removing CA glue. I had a speed controller switch that I accidentaly got CA glue on. Could't move the switch to save my life. I soaked it in Acetone overnight and the switch is as good as new. I never tried it on a balsa wing yet, so I don't know if the acetone would have any bad effects on the balsa. I would try a test piece first.
Joe