Tricky Dicky writes:

I have used a Multitool with those diamond edged
semi-circular blades to make capping wide chases for mains
cables. The Multitool is much slower than an angle grinder
but much less dust, it produces much neater edges to the
chase and does not disturb slightly loose plaster too much.

For fairly fine plaster or plasterboard a multitool with a
coarse sawblade is much faster than a diamond or grit edge. It
blunts the blade very quickly, but that doesnt make much
difference. Still less messy than an angle grinder. Wont go
into brick, though.

--
Jón Fairbairn
http://www.chaos.org.uk/~jf/Stuff-I-dont-want.html (updated 2014-04-05)