This kicks ass:
Pump-up pesticide lawn sprayer (clean) $9 at Wal-Mart
3/8OD, 1/4" ID tubing
Mister with plastic ballcock valve $5 at Wal-Mart
1/8" to 1/4" tubing adapter, found at Autozone in a "vacuum tubing" assortment pkg $2

Take off the sprayer handle (too big to mount on the headstock, and the handle would be hard to turn on and off) and tubing (it's too short), heat the end of the new tubing (as long as you need it to be) and press onto the fitting, join with the plastic mister tubing with the adapter. Use the little stopcock valve.

Figure out a way to attach nozzle to the headstock.

Now I don't have to worry about plumbing water in or getting a pump.

That'll hold at least a couple of gallons, even with a lot of space left for air pressure so the pressure won't drop too badly as it empties.

I started with one of those "personal misters". It was nice at first but had under 5 minutes of spraying capacity before the pressure drops noticeably if you're not pumping, even if you only fill it halfway so there's plenty of space to pump with air. That garden sprayer will probably have like a good hour's worth at least. I can get a bigger one if I really need it.

Interesting, what is the:

"Mister with plastic ballcock valve $5 at Wal-Mart"

Is this in the Garden center possibly?

Got a pic?

Thanks,
Dave

Found the mister in the clearance aisle. Actually it's the same tubing and ballcock valve in the little hand-pumped one, the only thing I preferred was it has a longer tube. Not that I can't add on as much 3/8" tubing as I like but the thinner mister tubing is more flexible and lays on the table near the mill better.

Not sure where it is normally. Could be in Sporting Goods. Actually Academy Sports probably carries something like this.

Now you guys just need to figure out how to run a compressed air line so you don't have to pump these up. I assume they're very low pressure. You'll want a regulator set to a low press to do it lest you rupture the thing.

Probably easier and safer just to convert it to an aspirator setup so you don't really pressurize the tank.

I have a pond size air pump that I'm thinking of utilizing until I finally get my flood system setup.

Dave