This has helped me - I trained take it with food (as part of take it and leave it standard stuff) and with toys (playing tug). I trained let go playing tug. The tug toy goes dead (or you trade off with a treat) and put the action of letting go on cue (mine is thank you). You get the dog to release whatever it is holding on the cue. I found this transferred from a toy to my clothes with no additional effort so if my puppy starts grabbing and pulling she will let go on the cue thank you. It's been the most helpful thing so far....I do still have to then distract her with something else, otherwise she starts again but it stops me getting into conflict with my puppy. Edited to add - I don't think I play tug like most people play tug. It is a very controlled game although the puppy does tug and have a good time. But I'm very careful about 'this is your end, and this is my end' and teeth don't come anywhere near my hand. I play with a toy on a bit of bungee cord, and concentrate very hard on it being a game about rules - you take it when I say, we have a good time, you release it when I say and then calm down. I also don't tug, the puppy does.
We did the same as Ella initially saw tug as a new, slightly more exciting way to get her teeth into my hands! We combine tug with catch so Ella tugs for a bit, then I ask her to let go and sit (I don't ask her to sit anymore as she knows it's the next step in the game) and I walk away to different spots in the garden and say "ready, steady, go!" as I throw the toy back to her to catch. She doesn't move a muscle as she catches it but as I start to say "ready..." her head stretches as far forward towards me as possible as she waits in anticipation! We then have a celebratory victory lap before she puts the toy back in my hand and the game starts again! It's by far our favourite game