My solution is currently on the Heath-Robinson side, I'll re-engineer it at some point.
I'm using copper brake pipe for air chip clearance, the nozzle was formed by crimping the end of the pipe in a 3-jaw chuck with a bit of piano wire down the middle to keep the required jet size opening.
I added to this an old-style adjustable drip-oiler with a length of tube directing the drips onto the chip clearance air pipe a few inches above the end. The result is fairly coarse droplet lube with no discernable contamination beyond the guards -



Apologies for the poor video, it wasn't intended for public release but hopefully gives an idea of the setup,
ATB,
Nick