If the unwanted paint chips are not near your blacklines
a q-tip with a little bit of alchohol will remove the paint.
But be forwarned it will also remove the lines on the
surface of the cel, so be very careful! This cel had a
very stuck top layer of flying rocks, the largest was right
over her face. I lost some black but it seemed to work
well. I tried scraping but the force required marred the
surface. Hope this helps.