The currants arrive on branching stalks. The most efficient way (in theory at least) to detach them from their threads is to take hold of the top of a thread of them, and dangle it over a large bowl or colander. Then with the other hand you run a fork down the thread from top to bottom and it pops the currants off the stalks.
Some will still have their tiny stalks attached, having popped off the main stem more easily than off their own stalk. These need to be fished out again and have the process repeated, either by fingers or with the fork.
Then run the colander under a tap to wash off dust and dirt and you're all set for the pan.