Back around the late 70's - early 80's when I was working in the bush, we relied on deliveries of fuel (diesel) by aircraft to run everything... generators, boilers, stoves/ovens, heating, tractors, the works. Fuel deliveries were once a month and a day hated by us all, despite the absolute necessity of it. By the end of the day, you would be covered in diesel, through your clothing, on your boots, through you hair... a stinking mess. Swannies couldn't be washed to get rid of the fuel -that would also wash out the natural lanolins, destroying the water-proofing and thermal insulation of the garment. The fuel just decayed over time, or was washed out by the frequent heavy rain! Diesel on the sole of your boots made life treacherous on wet rocks already slick with lichens and moss...
I digress. The deliveries were made by C-185 in 22gal drums. From memory, we carried around 10-12 per trip, with anything up to a dozen return trips a day. A tarpaulin was laid in the back of the aircraft with seats removed (only the pilot was seated!) and the drums wedged in tight so there was no movement in-flight. Not unusual for a passenger to be carried, perched on the top of the drums, folded up like a 1/2-open pocket-knife! You wouldn't get away with that today!!! The flight was about 10mins each-way, landing on a rough gravel strip, deep in a mountain valley. If anyone's interested, the strip could be found on Google Earth at about S44 47 19.61 E167 45 10.51
The day was complicated by the fact the delivery tanker could not decant directly to the aircraft, so the process was usually to fill a tank at a service station, decant into 44gal drums for the trip to the airport, decant again into 22gal for the flight, then decant yet again, usually into 44's, for distribution to the various necessary points around the site! A long day... And yes, all that decanting was necessary, for various reasons.
I'm not sure how it's done today, although I would be confident that the fuel is still flown in -although probably as a sling-load under a fling-wing!
Not entirely relevant to the question posed, but still a DG in an aircraft -and an interesting solution to an awkward problem! I'm sure tinpis and others would be able to relate similar experiences!