My Yorkie is about 6 months old now and he has a terrible biting problem. My hands are literally scratched up

I know that puppies go through this teething phase but I need some more advice about how to stop it. Also, how did you guys show "dominance" over your puppy? He absolutely hates listening to me... unless he's really tired haha. My vet suggested that I hold him down on his back but I don't know for how long or when I can let him go? help!! thanks!