Micheal I'm with M_C on this.! Keep the air to a minimum other wise you'll need a large CFM compressor and tank. Low direct pressure is all thats needed to clear the chips enough to stop re-cutting then good vacuum will do the rest.
Re cooling the spindle (which is what I think you mean when you say "indirect cooling") then I'd forget the compessed air route has the volume required would be large, the electricty alone of running a big compressor would pay for a water cooled spindle given time.!!
Maybe design some outer rap-around water cooled jacket type affair.??? Bit like an hot water bottle in reverse. .