Ive used a clay bar when I first got the car, and its amazing how much dirt these things lift off. I washed the car first, then used the clay bar and wow> the paint becomes glass smooth afterwards. The XF paint is very hard/tough and though clay bar cleans it well, it doesnt remove the swirl marks which if bad can look naff. I have a Mop which I have used on the XF's with good results. Damage is caused by having the speed setting too fast/high, applying pressure (non is needed) and allowing the mop head to go dry, and staying on one spot too long. The resulting friction then knackers the finish. Secret is, nice n slow, let the polish do the work, keep it wet, dont apply pressure, and keep the head moving all the time.