I made my first attempt the other day. I made 50 gallons.  Don't ask my why I made so much.  CH for about 2.5%  and 2 quarts of green wash.  I premixed the CH in buckets using a paint sock to strain.  After two rounds of that I tied the sock in a knot and tossed it in.  I then filled the tank using a nozzle to get thing agitated nicely.  Hosed down the grass and arborvitaes well, stuck a hose at a trickle in the downspout to dilute and went to town.  I have plant wash but I purposely didn't use it.  I wanted to get a 'baseline' without it since it doesn't matter if I kill grass here.  It's now been three days and no dead grass or plants.
I only cleaned part of the roof on the right for comparison purposes (my wife owns the building).  I'm happy with the results.  The black splotches on the clean side aren't algae.  Those are places where the shingles are so devoid of stone that they look black.  No worries though, this roof is getting replaced this summer.