Fuel flow capacity into an A380's tanks is about 6800 pounds (1000 US gallons) per minute, assuming compentent equipment. To fill absolutely empty tanks with the maximum capacity of 583000 lbs of fuel thus takes about 85 minutes. What with connecting and disconnecting the hoses and such, call it two hours maximum. (All figures dependent on fuel temp and actual specific gravity ("density") on a given day).
Beyond that, it becomes a question of "how long is a piece of string?"
How much fuel was already in the tanks? (Ideally, planes don't land on fumes anymore!) Does
one pump truck have to fill both wings - which means perhaps 20 minutes extra of connecting up the hoses twice, once for each fueling point? Does the airport have the ground tanks for direct pumping into the plane, or does all the fuel have to brought to the plane in individual tank (as opposed to pumping) trucks?
I'm not sure the A380 even
has gravity-feed (top of wing) fueling points.
https://www.youtube.com/watch?v=3BiYQbD-mVk