Step 1 - put the currants into a plastic bucket or bowl & crush them.
The blackcurrants for my batch of blackcurrant wine have defrosted overnight & are now ready to be crushed, per CJJ's first step.
Except that they are not are they? Close inspection of the bucket reveals that there are leaves & stems still on the blackcurrants due to lazy fruit picking back in July.
Actually, I'm not sure if leaving these in the mix will do any harm - after all, they will all drop to the bottom with the rest of the sediment in due course, but conscience dictates that I should pick out any stems and run a fork down them to ping the currants back into the bucket, & to fish out all the 'extra' stuff to leave just the blackcurrants in the bucket.
Well, what a tedious job that is, but it leaves a bucket of plump blackcurrants waiting to be crushed.
I've experimented with a number of methods of pressing soft fruit to extract the juice, & find that you can't beat using a potato masher (remembering to run boiling water over it first to sterilise). If I had a metal colander, I'd probably press the fruit through that - but I haven't, so the potato masher it is.
Once I'm happy that I've mashed every little currant, it's on to Step 2.