Why do I get swirl marks even though I hand wash my car?

Hand washing can still create swirls when dirt is dragged across the paint, the wash mitt is overloaded with grit, drying towels are contaminated or too much pressure is used. Most wash-induced swirls come from contact with particles rather than from the shampoo itself. Pre-rinse or pre-wash to remove loose grit, rinse the mitt often, use straight-line passes with light pressure and wash the dirtiest lower areas last.