Stealth,
NEVR-DULL is usually a fantastic product! I apply it, let it haze and then buff off with a very soft terry towel or M/F cloth! Usually removes everything in it's path for me!
Now..for you problem....
For me..I would try a 50/50 water/white vinegar mix first! If that doesn't work, you can try the ammonia (60water/40ammonia)mix suggested by Andydq.
AS ALWAYS...TEST ON THE UNDERSIDE OF THE WING..in case the ammonia or even the vinegar has a etching or harmful affect on the wing! I doubt it will (the vinegar) and you might even want to try the vinegar straight???
So..make the mixture...pour or spray liberally onto a soft terry towel cloth, wipe with good pressure, and then wipe off with another soft terry towel! Then use NEVR-DULL after to bring the shine back up!