my husband uses the tool your talking about he got his from https://roofscraper.co.uk/, hes a window cleaner that also does roof and pressure washing. I did ask him why he doesnt pressure wash roofs as i think they look like brand new but he says pressure washing can cause some serious leaks and thats why he only scrapes the moss off not sure what he does after but i know he brushes on a chemical i think its biocide? it takes a while to change the colour of the tile from what ive seen and some just look ugly afterwards?