Before you do anything, move your car out onto the street. Remember, once you've painted the driveway, it needs to cure for 7 days. Now, sweep the driveway. Then mix some etch primer into a bucket of water and give the driveway a good scrub using a stiff broom. Let the primer sit on the surface for 10–20 minutes, then wash it off with a hose. The etch primer is a strong acid, so be sure to use the safety gear when handling it.