There are a lot of VW/Audi people who have configured home made FMIC sprayers using items from Home Depot and used the stock windshield wiper tank and pump. Only issue is finding a nozzle that'll create a fine enough mist. If the droplets are too large, the water will just sit on the IC and possibly causing even more heat soak. Check out VWVortex.com or Audiworld.com, and search for FMIC sprayers.

Cryo or other sprayers are dyno proven. Problem with CO2 spray is if some of the CO2 is ingested by the intake, it's negatively impact performace. Spraying NOS would be a different story, but would be more expensive to refill. If you've ever seen one spray, it looks like an evil dragon breathing smoke.