Hello.
Well I used one of those tripod water sprinklers set just above the tops of my fig trees. I used this method for the past two nights as a heavy frost was predicted. I turned the water on at 11:00 pm and let it run until the next morning when I went out at 8 am. The fig trees had icicles on the tip of the leaves and no frost damage. I have about two hundred trees and the temps went down to 30-31 degrees. I did not lose any trees and had no damage at all, so the sprinkler method does work!
Vito