Used the clay mitt today,not on my M,on my astra work van,which was covered in tree sap,tar etc,haven't cleaned it properly in ages.
was a bit hesitant to be honest,thought it might not be as good as the traditional clay bar,but it did a great job,& was so much easier & nicer to use,after I'd finished it still looked like new,will definitely be using one from now on,no more clay bars for me,although I will buy a fresh one for the M.