My sister has just got a puppy - not a cocker I have to say.
It is, naturally imo, biting everything that moves at the moment. It is getting a little rough when playing with hands, and I have advised her if that is the case, to stop the game. I have also advised her to get it used to knowing what is acceptable to bite and what is not, so lots of reward and praise when it bites it chew toy etc and none when it bites their hands.
However her friend has told her that when he bites - which he is going to do for some time - she should make a fist and put it further into his mouth, as he will not like it. Also she should do this with any inappropriate item he bites. I am horrified and told her so.
Why would you do that to an 8/9 week old pup? They all bite at that age.
I think that at this stage it is important for puppy to bite - that he needs to learn bite inhibition and also that he is learning about his environment with his mouth.
I don't know very much about Cesar Milan, apart from what I have seen discussed on here and other forums. I have never had any desire to read his books. I don't know if the above is the type of thing he recommends or not, but I really don't agree with leading a dog through fear. They have to be led with love and kindness, within appropriate boundaries.
But I know many people think I am mad.