Need to repaint the outside of the house, the old masonary paint is
flaking off, though some bits are still sound. Manually scraping or
wire brushing two windowless, 8m wide, two storey gable ends and
another 10m wall doesn't appeal...

I'm thinking that a compressed air driven needle gun is the way to go
but not sure how vicious (or not) such a device is. The substrate is
stone and the pointing may well need looking at and chasing out in
places before repainting.

So is the needle gun a good idea or is there something better out
there?

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Cheers
Dave.