Yea...be real careful with the thinner, you don't want to eat away at your clear coat and then your really screwed. Understand you don't want to cause trouble, but this is his fault, his responsibility...plus if he becomes an A55HOLE, too bad!!!!
Every time I do anything outside that could remotely cause for stuff to blow over to my neighbors I go ask them if they could move their vehicles into the garage or down the street just to be safe...I get smiles and thank you's all the time.