Over the past year or so quite a lot of moss has grown on my garage
roof. It is pretty much a very big sponge.

I've had some success by shovelling a few spades at a time into a big
container full of water and then gently fishing out the moss with a
rake. But that's nowhere near 100% effective.

Ideas and what should I do next?

--
AnthonyL

Why ever wait to finish a job before starting the next?