They will Job it out to a local workshop anyway dealerships dont do paint?
I would get it done under warranty then--if its not up to standard they will have to keep on doing it until it is .
its all under warranty so why wouldn't you throw it back at the dealer?.
Book it in, give them a written list of work to be done and arrange a loan car from them.
Sit back and wait for your gleaming, fixed car to be returned.
Simple
Apparently it has to finalised by Mercedes if they approve it to be of a worthy warranty repair