What is the best product to use as a car wash? The correct answer is use what you like the best. There are some drawbacks to certain products and advantages to others. Dish detergents (Ivory Liquid, etc.) may be used, but realize that these products are designed to remove animal or vegetable fat from fired ceramic. They look at your nice coat of wax with the same hungry eyes. If you enjoy washing and re-waxing weekly, then dish detergent is for you. Wax retailers love people who use Ivory Liquid (they send the Ivory Company Christmas Cards every year).
If you prefer to have your wax last a lot longer, you may consider using a product that is specifically designed for automotive use. The quality products are based upon detergents instead of soaps. Most soaps are manufactured from rendered animal byproducts (the stuff the dog food people reject). They contain trace elements that can actually damage your paint. These trace elements are the same goodies that leave a ring in your bathtub. The exception is soaps manufactured from plant fats. (These leave mold in your tub - just Kidding)
Quality car washes/shampoos (same thing - most cars don't have hair) are usually pH controlled, contain gloss enhancers and some even have small amounts of water-soluble wax for good measure. Use only enough car wash to break the electrostatic/ionic bond between the dirt and your car. Start with a clean large bucket (preferably plastic - if you kick the metal bucket, Mr. Paint Chip rears his ugly head); add a small amount of the car wash and fill with cool water. Avoid hot water, as it will soften the wax. Read the directions on the car wash bottle and try reducing the recommended amount by half. I use less than a cap full in 5 gallons. The more car wash, the more wax you remove. Try to avoid powder car washes as the undissolved granules can lodge under your sponge or wash mitt and scratch the paint surface. Make sure that your car is in the shade and the paint surface is relatively cool. Rule of thumb #1: If you can comfortably hold your hand on the hood, you can wash/wax the car.
Spray the car with a gentle spray to thoroughly wet the surface. Don't use a 200 P.S.I. fire hydrant spray, it isn't needed and may grind the surface grime into the paint and cause scratches. Some of the concours purists will not use a nozzle on the hose at all. Start at the top of the car and work down. Rewet the top; gently wash the top and then rinse. Move onto another section, such as the trunk or hood. Rewet this area, wash and rinse. Continue on down the car, completing a section at a time. This way, the car wash does not dry on the paint.
You may use a wash mitt, wash pad or sponge to wash your car. I prefer a wash mitt, as the grit tends to work up into the long fibers and not scratch the paint. When I redip the mitt into the wash bucket, I give it a swirl to release the grit and every so often hold the top open, allowing it to fill with water. I then lift straight up and as the water runs out, it "back flushes" the trapped dirt out of the mitt. The flat surface of a sponge can sometimes catch dirt and act like sandpaper. The purist will use two wash mitts, one for the top half of the car (the cleanest) and one for below the trim line and wheels/wheel wells.
You should dry the car as soon as possible. There are several methods to accomplish this. Lots of towels are a great drying medium. They should be 100% cotton. Check any towels carefully as most towels contain polymer fibers that scratch like hundreds of hypodermic needles. Do not assume that the 100% cotton label on the towel is telling the truth. The only way to check is to actually set fire to a rolled up corner of the towel. If you get a clean flame like a candlewick then it is 100% cotton. If you see black smoke and melted fibers, then you got one of the non 100%, anxiously waiting to scratch your paint type of towels. One person checked 130 towels all marked 100% cotton and discovered that 12 actually were. I love truth in advertising.
Start at the top, lay the towel on the top and then GENTLY blot up the water from the surface. Change to a dry towel and blot any remaining water. Move to the hood or trunk and repeat. Dry the sides last, as the water will usually take care of itself on these surfaces. Another method is to use a chamois. There are two types, natural and synthetic. The natural leather chamois contain acids, primarily tannic, that strip wax. Most synthetic towels don't seem to do a satisfactory job. One exception is the P21S Super Absorbing Drying Towel. I have stopped using towels after trying this goodie and I used to be a "dyed in the wool" towel man. Driving the car to dry it may be fun, but you are re-depositing dirt on the wet surface and allowing the resulting "mud" to dry on the paint.
Bird presents are one of the most damaging "natural" disasters that attack our paint. (I have never seen a Yugo attacked by a bird, but just wait till your brand new pride and joy leaves the garage, they swoop in like someone rang the free birdseed bell.) I don't know what we are feeding the birds, but what comes out of the south end of a northbound bird is highly acidic. The longer we leave these psychedelic bird presents on our paint, the more damage they will cause. The acids tend to etch a microscopic pond shaped depression in the paint. Removal as soon as possible will help minimize the damage. Instead of carrying a hose and bucket in your car, carry a bottle of no salt seltzer water. No salt seltzer water is nothing more than water and carbon dioxide which will not harm your paint. When needed, take off the cap, place your thumb over the top, shake well and you have a fire hydrant that will wash the worst of the bird's thoughtful gift from your paint. Try to rub this area as little as possible. Birds use gravel to digest their food and grit is one of the major components of their presents. If you try and rub off the solids, you may scratch the paint. Once you have gotten home and had a chance to wash the area with car wash, rinsed thoroughly and dried, use a little Meguiar #34 or One Grand Show Off to help remove any leftover acids. When you have the time, give the area a coat of wax. If the acids have left a slight mark in the paint, see the article on cleaning your paint. 3M Imperial Hand Glaze will usually remove all traces.