So many questions to ask you, so many comments to make, I don't know where to start.
Are your friends cats neutered? That will stop the problem occuring again.
Have you got the cats now? Where are you keeping them? It is good that you are getting them vaccinated, but I would not have put Rabies at the top of the list. Where do you live?
As for socialising - I help to keep an eye on some feral cats that we call the 'car park cats' (they live in an old shed on the edge of a hotel car park) It backs on to a friends garden. Most have been neutered through a local charity scheme. Trapping and neutering was the only contact they had with humans - not ideal.
Over the months, when I fed them, I waited until they came to me and stayed with them while they feed until they got so use to me they would take food off me. I have reached the point now where I can stroke and fuss some of them. They keep me company when I am gardening!
I did the same with our cat Thomas. He was almost wild when he came to us. I would not feed him unless he let me touch him - just a little stroke to his head at first. Now he is a lap cat!
It takes time and patience, but it is SO worth it. I'm sure other, more experienced, Cat Chatters will have suggestions for you. Good luck
Sometimes I can't see the wood for the trees. 
