Yeah, "tokyo tanks" were fairly common in the Pacific due to the long distances, big problem there is you can't carry much of a war load when you're carrying fuel.
I googled this sucker, couldn't find anything about the US navy doing it in WWII, altho they fiddled with the idea in the '50s:
http://www.navsource.org/archives/08/08362.htm
http://en.wikipedia.org/wiki/USS_Guavina_(SS-362)
One pic in there of refueling a P5M at sea, scroll to the bottom.
Don't have any first hand experience with this, but thinking about the floating of oil drums across - seems to me you wouldn't need rubber boats, fuel is 6 pounds per gallon, water is 8 pounds per gallon, would a 55 gallon drum of fuel float by itself?