On Sun, 1 Apr 2018 20:15:11 +0100, newshound wrote:

And a manual brush at that, I suspect that a cup or disk brush on an
angle grinder may leave unsightly swirls.

Not sure where my manual wire brush has gone... and yes I think a
powered brush is likely to be a bit too vicious but a manual brush
hard work!

Needle gun ide came from a friend over in the next valley who used
one to clean the exterior walls of his place. So I think the stone
will withstand it, I'd go gently to start with anyway.

--
Cheers
Dave.