I bought one of these recently
http://www.ebay.co.uk/itm/Saving-Mis...item4198a99ef0

I have yet to try it out on a machine, but it sprays water quite well. I thought it was worth a punt for a fiver. My only concern is that there may be a lot of mist droplets floating in the workshop air. Water isn't so bad (for my lungs) as sudsoil mist, but unless you ventilate the shop properly I would expect rust on any exposed metal. I seem to remember a discussion about (low fog) misters.

If you are using a dust commander then droplets of coolant are likely to be separated by centrifugal action, but a more dedicated device such as a knock-out drum, where there is enough space to allow gravity to separate the drops in a vessel large enough to slow the airflow, would be better.

For cutting wood or MDF then the dust commander would be better, but I can see that the cyclone effect would be easily buggered up by wet oily deposits in the cone, when the dust sticks to it.

To me it really looks like you need two separate systems for ali and wood, I don't believe you could make one that would do both properly.

Cheers,

Rob