www.sprayandforget.com

That looks like it might work. Results show after a few weeks.
Needs no scrubbing or rinsing and lasts for months.

Thanks



While I agree with what they say is the problem, they are trying to rope
you in to keep buying the stuff.

"A standard practice should be to clean your roof and then apply a
preventative such as Spray & ForgetTM every 18-24 months"

I would never consider cleaning the roof if it involved any physical
pressure on the grains in the shingles. The above product does not
require scrubbing or rinsing. It only requires a time period for the
results to show.