Luke like Vombil said a safety blade does the job, i find the trick is to hold the blade 90 deg to the rubber and run it lightly over the overspray so you don't rip or damage it and then run a bit of rubber dressing on to bring it up like new.

Cheesygrinner overspray on paint will come off with wax and grease remover if light however if that doesn't work you may need to run a buff over it you will find it comes off quite easily but in some (extreme) cases may need a slight rub with 2000 grit before hand. Overspray on un-tinted windows come's off with a bit of steelwool (soft grade) or a safety blade can be also used just run it almost parallel over the glass.