Cleaning/developing

Admittedly this is a stupid question but it's not a troll. I'm taking the chance that someone has some brilliant trick besides "big brush and sack up."

I'm looking at a big job: developing a bouldering spot with a lot of moss. This place is sweet and worth the effort, but a power washer is logistically out of the question and I don't want to use any herbicides.

Don't forget the dust mask and goggles. Mission critical.

Electric drill and wire (if really hard rock) or plastic wire brush head?

And, if it is just moss -- be happy. That generally comes off a lot more easily than lichen! (Of course, it grows back faster, too.)

Also, I so envy route developers in a desert climate, where the rock is just naturally bare.

If it's granite (aka: not soft stone) I've used a cordless powerdrill with a stiff nylon scrub attachment on the end. similar to this: scrub brush attachment