In reply to k.e.urquhart:
Wire brush should be fine fine unless it's particularly soft rock, such as sandstone. Most of the rock up your way Schist or Conglomerate, so shouldn't be a problem on that front. Only issue would be if the venue is a SSSI (Site Special Scientific Interest) where the designation identifies the presence of a particularly rare moss or lichen, and should be protected and left alone.
On your doorstep, Creag nan Clag (The Camel) at the southern end of Loch Duntelchaig would provide some great long mid-grade sport routes on the front face; unfortunately development is restricted to the already developed area on the gully wall, due to a rare lichen, I believe.
In contrast, was a bit underwhelmed by our visit to the Tynrich Slabs, by Loch Ruthven last year. Thought the write up in the current Highland Outcrops South bit overenthusiastic - many of the starred routes were pretty dirty. Surprising, as it's very convenient from Inverness, with a good spread of grades.
