For me, the simplest and most convenient way to balance the ailerons was
to build a jig for each one. The jigs were designed to duplicate the
aileron position on the wing in neutral position, in trail at the
wingtip. With the aileron in the jig, you can continue adding weight
without having to constantly remove and reinstall the aileron on the
wing to check what you have done.

Angier Ames