In general I find pruning different bushes confusing and it seems to take ages of comparing photos and diagrams to decide which branches to cut. But I've figured out the red currant for now so here goes.
I bought this bush in mid 2006 and here it is the following spring(2007) just as it started to bud. When I got the bush the two long(main) branches you can see above were longer. The norm might be to get one with three or four. Anyway, what I should have done was prune it immediately as this encourages growth. I didn't and the thing did not grow at all. There were a few measly leaves on it all through the year and that was it. So in its second winter I pruned it so that it looked like it does in the above picture. I cut the two branches by one half of their length.
The difference this made was incredible! This is it in May of the same year with loads of new shoots and leaves. If it hadn't suffered from wind damage it would have gotton a lot bigger. So pruning actually does promote more vigorous growth.
Here is the same bush about 8 months later in January 2008
(You can see that the some of the branches are all wiggly on this bush because it suffered from wind damage when this years shoots were still very young. They almost snapped at the join and I staked them upright again hoping they would survive. Most of them did but the had already gone a bit funny as they weren't sure which way they were supposed to be growing.)
I have read that you should mainly be prune red currant bushes in late winter. If you have a problem with birds eating the young buds then hold off for as long as possible so as to decide which branches to take off etc. I suppose if all the buds have been eaten off you should just take this one out, giving more space to other branches.
PRUNING THIS BUSH....
The first branch to go was the right most branch you can see above...the large one that starts at the bottom of the plant. All branches that are within about 10cms of the ground should be removed so as to encourage a good framework. Each type of fruit bush seems to need a different shape in order to help the fruit flourish.
At the start of the life of the bush you want to start choosing upright branches to keep. You want four good strong ones to start things off. There are two obvious contenders here and so I thought about those first. You chop half of your chosen branch off. You can see the before and after shots above. Remember to cut a slightly slanting cut so as to prevent a build up of water on top of the branch.
I then did the same with the three other branches than looked sort of like main upright stems. Compare this to the bush before I pruned it.....You will notice that there are two side ways branches unaccounted for. Well, if you look closely you will see two very short "spurs" on the left most branch nearly half way up. These were pruned differently because they were off shoots of my chosen main stem. Any side shoots should be cut back so that there is only one bud left on them. These will be the fruiting spurs for this spring. I have only two :(
This is not unusual and it will be next year before the fruit is set up for fruiting. There is now a good frame work on the plant which you develop from year to year, basically repeating the same process.
I hope this is helpful...it may all sound confusing but I have found that if you keep comparing the before and after photos and just start having a go that you will get the hang of it.
Remember to stake any new growth so as to protect against the strong winds. Putting your pot in a sheltered position would help. One of the advantages of keeping fruit in pots is that you can move them around depending on the seasonal requirements.
Here are a couple of photos from the book that I have been consulting about this. They might help.