Back then..... I used to eat, live and breath on drum stock. These days probably do not see that much of it and I am sure many of the people teaching in the flying schools may never have seen one.....
Be very cautious - and if in doubt as to the contents, age and quality of the fuel - DO NOT USE IT. Particularly refilled drums that you have not filled yourself. Be very wary of the leftover half a drum from god knows how long ago.......
If using drum stocks be aware that drums exposed to the elements will become hot, a sharp shower will create a vacuum in the drum drawing in water from bung seals, ensure drums are placed slightly of vertical with both bungs clear of any possible water entry.
....spot on-ski. Storing of the drums - we kept them horizontal off the ground on wooden racks. Bungs tight and located in the horizontal plane to prevent sucking and expelling air/water by being covered with fuel. When mobilized for use - place drum upright with a chock under the point where you are drawing fuel from - ie water drains to the lowest point in the drum and NOT where you are drawing it from. "the fuel broomstick" with some water detecting paste inserted into the drum will give evidence of contamination before it is too late.
In any case - the Canucks have a short brief on their website:
Fuel Drum Etiquette (TP2228E-13) - TP 2228 - Take Five...for safety - Publications & Videos - National Operations - Aviation Safety - Air Transportation - Transport Canada
and a short CASA one:
HTTP://www.casa.gov.au/wcmswr/_asset.../mar/32-34.pdf
....and good that they also mention grounding for refuelling - as the number of times I have seen slack-arses not do this - even when using a bowser....
Take the time with drums and do it properly.