One thing to be aware of with stain removal is many times depending on the mineral composition and level of deposit, many applications with different chemicals or with more abrasive pads and buffing machines may be necessary.
I’ll add another month later complaint…did a job w several condo units. All was well, did gutters and windows. Property manager emails this morning that ex unit complained that we didn’t do their gutters. Fortunately we are in the area next week and it’ll be easy to check out. But two things: tile roof, with the tiles partially covering gutters so I know that messes with flow and 2, it was a month ago! Sheesh, I need to come up with some time limit for complaints.