i read a study from the univ of texas showing that handwashing was worse than running it through an automated car wash. dont see how this is possible. especially if you stick to using MF rags/mits and good products.
I have been using MC fiber towels I get at Target. But it does not matter what you use if the dirt/grit comes in contact with the paint. It will cause very small scratches. Over time they add up and the paint becomes dull. And, if you think about it soap and water is supposed to cut wax, grease, oils and any other type of protective lubrication. Every time you run the soapy rag across the surface of your paint it drags the grit right on the paint. For the past three years I have been using an acrylic polymer wash on all my cars. If you have regular dirt (not off road mud) it works great. The wash provides lubrication and the acrylic is harder than wax. I also use a synthetic clay bar about once every 6 months to a year. It makes the paint so slick it almost feels wet. The brand I use also has high UV protection.