Thanks Karl,
While I don't have a MIG tip I did get a small selection of nozzles with a blowgun I bought a while back. From 2mm, 1mm, down to 0.75mm. That small one I think they call 'needle' tip for some kind of valve on a sports ball.

Could even go down to 0.5 or 0.3 mm. I have managed to take the ball out of some empty metal ballpoint refills and the front section of those refills fits nicely into the 2mm tip.

I suppose it's now trial and error time although I feel that the 0.3 and 0.5mm tips will be too small to be of use