you might have to wetsand the spots where the spraypaint is till it's gone then give the complete car a good buffing. Before you do that go to a body shop and ask if they make anything to remove spraypaint off your car's paint or ask a autobody supply store the same ?
I know you will think this is crazy but years ago, one of the guys from the old neighborhood had his van vandalized on night. It was a blue and white two tone. They went down both sides with a black spray bomb. My buddy removed that black paint without damaging the white or blue. He used salsa and a whool buffing pad. No I am NOT joking. I don't know if that's any better than compound, but it definately worked.
A friend of mine's car got vandalized a while back. I used laquer thinner to remove the spray paint. It was a newer car with clear coat paint though. I washed it immediately after, and then waxed it, as the solvent strips all the wax. Came out great
i own a detail shop and i use clay bar alot on overspray cars its safe and easy to use wax the car after you use it and it will be the smoothest and brightest paint that you have ever seen on your car claybar is a awsome product.