Castrol Super Clean will take off paint like nobody's business. Maybe a little on a Q-tip will get the smudge off. I haven't tried it on clear plastic, so try it on some scrap first.
If you want to replace the canopy you might try some Thermo Form. I've never used it, but it's a sheet of clear plastic. Heat it with a candle, pull it down over your old canopy, and it will form over it. Let it cool, cut it out, and you have a replacement canopy. It's available from Squadron (www.squadron.com)