Dean - Thanks for the input. I realised the ones I linked to are used the venturi principal which atomises the droplets. This is the effect i'm getting at the moment using my cheap airbrush setup
And you're right, the fine mist created is horrible and fills my little shed in minutes! I was thinking of using the mixing block etc from one of those systems but feeding it from a pressurised coolant container.

Silyavski - Thanks for the link to those plans. I'd seen them before, but they were linked to from this thread. Karl_T recently modified that system as it didn't work well with air-blast only (see post #64).

I like your idea of using the compressor's tank as the coolant dispenser. My only concern would be that you would get water mixed in with the coolant (not a big issue) but you're also likely to get rust particles contaminating/blocking the coolant line.

My preference would be to have 2 regulators coming from the main tank outlet, one for air pressure, one for coolant pressure. Feed the coolant line into one of these (as shown in the link above) then to the mixing block and run the air line directly to the mixing block.

I'm also thinking that it might be beneficial to have 2 lines/nozzles from the mixing block rather than one. I think that 2 nozzles at 90º to each other would be more effective at clearing chips from deeper slots when using air blast only. Maybe one for air and one for mist, with the option to use both as air only.

I'll keep reading and searching suppliers to see if I can come up with plan.