Rubbing alcohol works on tape residue, but not overly
quickly. The way I've used it is to put the alcohol on a
Q-tip and work slowly from one end of the tape residue to
the other, turning the Q-tip as I go. You'll need to change
up the Q-tip fairly frequently. The alcohol will make the
residue very soft and the residue can redeposit onto the cel
if you don't change the Q-tip when it gets sticky. (Does
that make sense?)

But it does work! Just watch out for surface paint and lines
because the alcohol will erase them too. . . (Blah, blah,
blah - I know people have beaten this into the ground but I
better say it anyway before someone claims they didn't
know. . . ^_^;)

Many Sharp Smiles,
--Drac