Taking proper steps in washing your car can enhance the effort of detailing. Proper washing will keep contaminants off your paint finish and reduce dulling and deterioration of the paint finish.
You should never wash your car in open sunlight. Also make sure the vehicle is cool. Wash water and rinse water evaporate too quickly from a hot surface and leave water spots which are salt and mineral deposits. Such deposits can eat through wax and etch paint if left on the surface for any length of time. Use lukewarm or cool water. Water which is too hot or too cold can cause a shock to the paint and lead to microscopic fractures of the paint surface.
Never use household detergent -- powdered or liquid -- these products are formulated to clean clothes, scour metals, plastics, and porcelains to remove grease and oil. The mere fact that a detergent is advertised as being gentle to your hands does not mean it is gentle to your paint/wax finish. Many of these products have high sodium or alkaline content and are too strong for automotive care. They can accelerate paint oxidation by removing exising wax and depleting the oils from the paint. Use a pH balanced or neutral (pH7) detergent on your car. Always check the label of the product you are using for a listing of all the ingredients. You are better off using too little product than too much. Too much detergent will leave a residue if not rinsed off thoroughly.
Detergent both cleans and provides lubrication between the sponge or mitt and the painted surface.
Wash the car from the top down. Some detailers use different sponges or mitts for the upper part of the car from the lower part of the car since there are more dirt particles on the lower part of a vehicle from closer exposure to the road. Rinse the car often during the washing process. Use a large bucket such as an old 5 gallon joint compound bucket or a plastic bucket from your favorite local donut shop.
Adding a teaspoon of vegetable oil to the washing solution will assist in carrying away the dirt particles from the painted surface.
Use at least a couple of towels to dry your vehicle -- one to quickly push the water off the car, the other to thoroughly dry the surface. Open all doors and lids on the vehicle to enable semi exposed areas to dry completely. If a chamois is preferred for drying, use only an English Cod Oil-tanned chamois. Other chamois may remove wax and eventually scratch the paint surface. Synthetic silicone-free chamois are available for quick and easy water removal from the car. In any event, the final drying procedure should be done with a cotton towel.