I second Will and suggest Bug and Tar Remover. Bug and Tar Remover is perfect for removing the overspray from that stuff (and a ton of other things) especially when it hasn't completely dried. I had a lot of overspray when I undercoated my wheel wells in the Fall (I actually did a lot on purpose to see how well it cleaned it off
) and well, it'* amazing stuff.
If the overspray is dried, it will still come off. B&T remover also removes any wax that was on the paint so a coat of wax afterwards is a good thing
I always stock up on a couple bottles of this stuff in the spring. I couldn't live without it.