I've just come through exactly this. Nothing seemed to work at all. But with persistance standing up or walking out of the room works. If pupst goes to bite someone else, they stand up and show her no reaction.
What you need to remember is dogs sense and feel with their mouth. They have no hands. Humans hands are full of very sensitive nerve endings which tell us alot about something new; the texture, weight, shape size, etc. Small puppies learn by mouthing. Cockers, due to the original nature of the breed are known to mouth more so expect some weeks of bitten hands, ankle, etc. They are sensing their environment and they are also scared.
Now, I really appreciate how painful this is. I have had three Cockers and you very quickly forget those few months of pain, and it was as much a shock for me as for a first time owner, as the intensity of Tali's biting has been very bad.
But standing up, leaving the room, etc DO work eventually. Tali learnt all the basic commands; sit, stay, down, drop, leave, come, etc, in a couple of weeks. No biting however, took far longer. But their IS an end, Tali has lost all but one baby canine now and I have been working very hard on the gentle command and he can now mouth my hands softly. Yes he still tries to have a chomp but we continue with the training. With my previous dog I could remove a treat he was chewing from his mouth and place my hand in there and he would push ,y hand out. He had no intention of ever biting me, but it takes time and practice.
With regard the baby teeth, around 17 - 21 weeks all the sharp needle teeth should be gone, and you will then understand the expression, "velvet teeth".
Please don't forget your pupst is scared, inquisitive and very, very young. I know it's painful, but you will get out of you pet what you put in.
If you do feel you cannot cope, speak to your breeder who may be able to help or rehome the little dot before she's too old. But please be REALLY sure before you uproot puppy.
PM me if you want and hope that helps.