You will blow the sand out with a pressure washer.
You need kiln dried sand to go back in, and the joints have to be perfectly dry, otherwise the sand gets damp and wont trickle into the joints.
It's a heat wave kind of a job.
The other alternative is get on your hands and knees with a scrapper, and scrape the moss out.
There is even a proper tool for such a thing.
Truthfully, there is probably not a great deal in it, time wise.
Maybe pressure washing with a jet is a bit quicker, and more pleasant, but then you can end up leaving streaks on the bricks, which looks unsightly.
Other alternative is some kind of scrubbing attachment for the pressure washer, but then your talking more money, and you'll probably have to re sand it anyway.
I'd scrape it off and re-sand, myself. Done it loads of times, for other folk.
It's surprising how quick you can clear it, once you get into the swing of it, just plays the back up a good bit, I find.
'Oribble job..........
