Create a no-cost collapsible spray booth to store in your garage. (See photo at the end of the post). This not only keeps the overspray from going everywhere, but it is also a place to spray paint when it is too cold to go outside. Just be sure to open the doors while you spray and then close them when you are done.  Also remove your cars from the garage. Trust me... overspray happens. You can find large boxes in the dumpsters behind retail stores.