Cleaning Asbestos Cement board siding
We have a late 1950's split level in suburban NJ with what I believe has been referred to as asbestos board cement siding. One of my elderly neighbors (original owner) recently had a fly by night painting service come to his identical house and did some sort of powerwash/ sanding process and then paint it and it looks terrible. It has shiny spots, rub spots (visible from the street) and it basically looks like a fly by night job.
We are not well off enough to get new siding nor painting but want to get the green "shotgun spore" build up off of the north side of the house and clean various other dirt which makes it less than spotless white around. My wife wants the guy who cleans out our gutters to powerwash the house while I am concerned that powerwashing might chip or be too abrasive on the ancient siding.
What is the best way to clean this style of siding?