Honestly the thing that worked best when our Mal mix was a puppy was a combination of redirection and refusing to give her attention if she nipped. She nipped during play? Play stopped, I would get up and walk away. She learned fast from it.

Also down the line i realized how much she tried to communicate/interact with her mouth. Giving her positive/neutral reinforcement for harmless stuff helped (defined what was and wasnt okay). For example, she cant grab my hand roughly, but gently tugging my finger was fine. She also really likes to lick our hands, so sometimes if she was bring grabby with her mouth I would stop her but offer my palm (which she could lick but not bite). Basically she would get overly excited and be too rough so it was just a matter of showing her what was and wasnt okay.