Clean Paint is Bright and Shiny
Often it takes more than just a wash to get your paint clean. Bird droppings and man-made pollutants settle on the paint and, after a while, can saturate through wax and clear coatings into the color coat underneath. With your car still out of the sun, run your dry hand across the surface of the paint. If it feels rough, it needs to be cleaned.
There are two ways to clean contaminants, as well as stained and scratched old wax, off your paint: chemically or physically (though Pennington says it usually requires a combination of the two). Paint cleaners are liquids that remove wax, and also clean the top layer of the paint by removing unwanted environmental chemicals that have bonded to the paint. Cleaners can also remove small scratches called swirl marks from the paint.
The second method is to clean paint by rubbing a small block of paint-cleaning clay lubricated with a liquid cleaner wax. "It's a safe way to remove contaminants," Pennington says. "You don't need a trained person or a machine." Just make sure you don't use a piece of clay if you have dropped it on the floor.