Washing only removes surface dirt. To remove deeper oxidation, minor scratches, and old wax you many need to use a polish or more aggressive rubbing compound before waxing. Polishes use abrasives and/or chemicals to rub off the very top layer of finish, so don’t overuse them. On clearcoat finishes only use a polish that is specially formulated “clearcoat safe” and nonabrasive. If a polish rubbed between your fingers feels granular or gritty then it definitely contains abrasives and should not be used on a clearcoat finish. Always read the product label for specific recommendations.