That’s not a job for an inexperienced person , there is so much that could go wrong. , drift from overspray , working on the pavement and road , hypo mix going onto cars parked near by , and pedestrians, are you insured for Softwashing ? If you are unsure of what to use to clean it it would be best to walk away from this one and try a bungalow, or something smaller until you have a bit of experience.