Spray and Walk Away. I’ve used it on a couple of projects. Apply with a pump sprayer, so little to no run off. It may take weeks for the moss to go away, but it doesn’t come back.
https://www.homedepot.com/p/30-Seconds-1-Gal-Cleaner-Spray-and-Walk-Away-100506799/202897313?MERCH=REC-_-PIPHorizontal2_rr-_-206409694-_-202897313-_-N