I quick scrubbing with a cutting wheel on a Dremel should take off any overspray.
J/K. Look for any of many graffiti removal products. Some are extremely genial and easy to use. My boss used these http://www.graffitisafewipes.com/ on a show car he had. Someone painted crap on it, and again on a motor home someone shoe polished on a painted surface. Worked easy and without any trace of damage both times.
I had the same thing happen to me. Had some overspray in the air land on my bike. I got a clay bar kit and it worked awesome. Never know it happened at all. Actually I think it even made it look better Han the day I bought it brand new off the show room floor. Come off very easy also.
Have to go with the clay bar myself. They are amazing I had overspray all over my bike from another project. Was told it would have to be repainted so I tried a clay bar and it turned out to look better than new.
The same exact thing happen to me this summer. Having the house and garage painted and over spray got on the front fender. I used a scratch remover to remove the over-spray and then applied two coats of wax. Looks like new again.