I am going to just 'wet' some distilled water with either glycol or isopropyl.
The only reason you would need to do that is for corrosion resistance in a steel radiator. If you use copper, you don't need to worry about corrosion as long as you use distilled water and acid-clean copper. If you can't do that, then use phosphor bronze instead of copper. Phosphor bronze should be more than adequate for corrosion resistance, even at modestly elevated temperatures.