a clay bar should remove that. (thats what they were originaly made for, overspray on cars bodywork, not for cleaning them) if its on glass a rasor blade or stanley knife blade will remove it very easely
you might want to use a more agressiave clay though. failing that you would be looking at 2000-3000 wet and dry then a polishing compound like g3 or g10 and a mop to remove the sanding marks that are left.
if your near me i can have a go for ya (lincolnshire)