I have been hired to tame this little girl's pet store rat. For months, none of his owners have touched him in fear of getting bitten. He squeals whenever someone strokes him and is very fearful. He won't allow to be picked up. He squirms and squirms and Im afraid of dropping him. He has never bitten to be mean, he just bites because he is afraid. He has never bitten me though. Any tips?