Max : I have only had 2 issues with brush damage in 13 years.
The 1st one a couple years ago, a gal put a deep scratch in the hood of her brand new car when the brush came off of the wand while she was washing the hood. The wand left a deep scracth .
That one cost me $400. Just a month ago a customer showed me his brand new minnie van with paint scracthes. Said he had washed the day before and the brush had lots of sand in it. He was not to happy. I showed him the signs that inform customers to rinse off the brush prior to using it. Obviously he didn't read them 1st. Told him I was sorry, but I could not take responsibility for the damage. If its my fault I pay, if it is not, I don't.