So many different ways and oppinions on udder washing. Wet cloths are not considered any good now as they carry bacteria from one cow to another and transfer infection. If the udder and teats are clean then some dont do anything. If they are dirty use a different cloth, disposable towel, wet wipe for each cow. The main thing is the cows milk let down response is triggered by what you do, so if you wipe each time then she will get used to it. So whatever you do keep the same routine. Cows love routine.