I did an FMIC water spray today but used a different method.
As I never use the rear wiper or washer I just ran the vinyl hose off the rear washer pump, out through the front bar and Teed off to 2 garden variety conical spray heads mounted just behind the number plate, one at either end. I put a one way valve just before the first spray nozzle (couldn't find one at auto parts stores or at Bunnings, so stole on off the wifes car )to stop it dripping due to gravity.
I then disconnected the 2 plugs that go to the rear wiper motor (under the rear parcel shelf) so that when you activate the spray (via the wiper stalk) the rear wiper doesn't go off.
With the 2 conical sprayers angled correctly the spray covers about 80% of the cooler which I reckon is sufficient.
I am planning to buy the smallest push switch I can find (not a toggle type affair) and see if I can somehow run it up through the gearknob or perhaps attach it to the gearknob so that I can give it a quick squirt at each gear change when running hard, rather than having to take a hand off the wheel just to spray.
I was a bit worried that with having the two spray heads "in-line" that the second one would not get enough pressure, but they seem to both be putting out about the same amount of water so all is good.
I will try to take some pics when I find a suitable switch, but for the moment I can live with using the rear washer function on the stalk.