well start with laquer thinner. soak a rage and let it sit on there... if that does not work move on to actone, fallowed by MEK... just be very carful with the mek... it will eat the clear, gel and to the glass if you let it sit. try some place out of the way and do some testing.
Sanding is sill the best method... 220 on a block should take it down pretty fast.