Freezing layers while finetuning

[bakszero]

Are there some pointers to go about finetuning only a few layers while freezing the others? Say, I just want to finetune the final layer while leaving weights for the other intact, etc.

A natural extension to this would be gradual unfreezing wherein for certain epochs -- finetune the higher layers while keeping other layers frozen, then unfreeze , similar to what ULMFiT (https://arxiv.org/abs/1801.06146) did. Wanted to know if the above 2 are possible here -- more so the first one, thanks!