It took us quite a while to get started, as it seemed like every time we'd get one problem settled, another one would come along. But eventually we got the heavy safety line hoisted over the roof (we keep a light line in place for this purpose -- this isn't the first time we've had to do this), a ladder up to the roof, and a second ladder on the roof hooked over the peak of the roof. Lisa then put on her safety harness and climbed up on the roof. This has two lines attached to it, so she always has at least one attached to the safety line at all times. But moving is slow because you have to unhook one and move it to the next attachment on the rope, then do the other one, and so forth.
For the next several hours, Lisa whacked away at the accumulated moss with a rake and a broom. Sometimes she would send me off for other tools, like a saw to go after branches of a tree overhanging the roof, which I would tie to a light line for her to haul up onto the roof. There was a lot of moss -- I wouldn't be surprised if it was a couple hundred kilograms if we could somehow accumulated it together and weigh it -- spread over that roof.
While up there, Lisa discovered a hole in the roof about the size of what you'd get if someone stepped through the roof. So, when she climbed down for lunch, we got some shingles -- she has stack of them under cover -- and we also walked over to the hardware store to buy moss-removal powder and nails. Lisa then climbed back up to the roof and nailed some shingles over the hole in the roof. Then she went after more moss. She got the worst of it -- the thicker the patches, the easier they come off -- but some stuff won't come off without taking shingles with it. So she spread out the moss powder over such of the roof as she could manage. Fortunately, the weather was just about right, although it was colder than we would like. Mostly no rain, and overcast, with no wind while spreading the powder, and then just as we were breaking down equipment and putting it away, light rain began to fall. (This is good because rain spreads the powder down the roof and keeps it from blowing away.)
I know it sounds lazy of me, but I can't go up there anyway. I'm too heavy for the ladders and am more likely to punch holes in the roof while blundering around. My job is to fetch things as needed, sometimes move ropes and lines around, and sit in the large riding lawnmower to which the safety line is tied to provide additional ballast
We're not done yet, although I think the worst is over. We left the upper ladder up on the roof because it's such a hassle to get it up there in the first place, and, weather permitting, Lisa will go up again with the safety line set in a different place so she can get as spots she couldn't reach today.
This is hard work -- harder for her than me, I think, but something that definitely needed both of us present, for safety if nothing else.