Washing your own car can be a fun job, if you do it properly and avoid scratching the paint. Car covers will do much to protect the paint job in between washings. Your car’s paint job is quite delicate, and anything more abrasive than a very soft towel can scratch the surface. That is why you need to be particularly careful when washing your car especially if you are taking it to have someone else wash it. Any dust or debris that gets onto the sponge can quickly scratch the paint causing irreversible damage.
As a general rule, I try to wash my car once per week. However, if tree sap or bird droppings get onto the paint, you will want to rinse them off immediately. Bird droppings contain acids that can eat through paint within a matter of days so it is crucial to get it off quickly if this happens.
If you use car covers, such minor mishaps are never a problem. In any case, a weekly washing will normally take care of the typical dust and dirt buildup that all cars experience. When washing your vehicle, don’t use the same sponge, brush or rags on the painted surface that you would use on the wheels and tires. So much debris builds upon them that if you use the same tools to wash the painted section of the car’s body, you risk scratching it. In some cases, the brake dust or grease from the wheels and tires can leave a nasty residue on the surface of your car's paint.
Generally speaking, never wash a car that has been sitting in the sun or is otherwise very hot. Heat dries the soap too quickly and can lead to spots. Sponging should be done in straight wipes, never a circular motion. Circular sponging can leave tiny paint scratches.
Before beginning the wash, use a hose to gently rinse off any excess dirt or debris that may have built up during the week. After that, start at the top of the car and work your way around the body. If you regularly use a car cover, you know that weekly washes are much easier, because there is not much buildup. Most people can even get away with going more than a week between washes due to the benefits of using car covers. Either way you go though, using a car cover will save time and money when it comes to maintaining the exterior of your vehicle.