The drive-through tunnel wash at the gas station uses a foaming pre-soak to loosen grime; a foam gun does the same thing. By spraying your car down with a solution of foamed car soap before washing, you are loosening and lubricating the dirt on the surface before you ever have to put your hand to the paint. I always advocate this step as it is cheap insurance to maintaining a glossy and swirl free finish. Although less effective, you can spray the car down with the hose before washing to knock off some dirt.
Foam guns are a ton of fun to use and way more effective than simply pre-rinsing.
A cool environment out of direct sunlight is crucial for a good wash, and even more so when using a foam gun. Keeping the surface cool allows the soap more time to dwell on the paint before drying out, which does a better job of loosening and lubricating the dirt off the car.
To begin the wash, take your saturated wash-mitt and begin wiping the body, starting with the cleanest areas of the vehicle. By cleaning the dirtiest areas last you’re minimizing the amount of dirt that gets trapped in your wash mitt as it gets dragged across the paint.
Begin washing with the cleanest areas of the vehicle first. I usually start with the roof.
The primary cause of scratches and swirl marks in your paint is from bad washing procedure. We wash from clean areas to dirty ones to minimize the scratch-inducing dirt that gets trapped in the mitt. It is inevitable that some dirt will get transferred (otherwise we wouldn’t be washing in the first place!) but there is no reason to make things worse by loading up the mitt early with dirt. There is always a chance that some amount of scratches will occur, even with good washing procedure. A good rule of thumb is to start with the top of the car and finish with the bottom, while washing in the direction of airflow (front to back). The reason we wash in the direction of airflow is so that any marring we may instill during the wash occurs all in the same direction, which is much less noticeable than circular marring.
Wipe in the direction of airflow, in the off chance that you DO cause some scratches they will be less noticeable in this direction. Also notice where my right hand is placed, I try to avoid toching painted surfaces whenever possible. Detailer habits die hard…
In order to get your car clean you have to use a clean wash mitt, this is why it’s important to clean out your wash mitt often. Dunk your dirty mitt in the rinse bucket and wipe it against the grit guard in the bottom or against your hand to knock off the accumulated debris. As a rough guide you should clean out the mitt after every 2-3 panels, for very dirty vehicles it may be wise to rinse it out more often. Follow that up with a bath in the soapy wash bucket and keep on washing.
Clean your wash mitt often, after every 2 or 3 panels.