I do my own, with no training, just guesswork, nbased on what I see, plus what I learned at Chris Tucker's RCIA and RCIA.ORG
To see my results, look up BERGMAN ROOF CLEANING ans add my local towns, counties or zip codes, like BERGMAN ROOF CLEANING PORT CHARLOTTE - or BERGMAN ROOF CLEANING CHARLOTTE COUNTY, OR ROOF CLEANING CHARLOTTE COUNTY-Or 33981 or 34224 or Pressure Washing the same. Here is PRESSURE WASHING CHARLOTTE COUNTY- https://www.google.com/search?sourceid=navclient&ie=UTF-8&rlz=1T4PLXB_enUS731US731&q=pressure+washing+charlotte+county