Not much to add.. just some comments.
On dremels, for a long time they had warnings not to use on dogs, lol. Then they made one for dogs.
For dogs that hate nails, do one a day, fast, over, no trauma. After a bit, do 2 a day. Eventually they'll adjust to all being done.
As for growling... how else can they tell you they aren't happy? Do dogs that growl then bite? Um, yeah, some do. Usually if you ignore the growl and keep pushing it, especially if you are scaring or hurting them. The smart thing is to figure out why they are growling and either don't do it, or work on helping it be less stressful for them. Some dogs growl over everything because they learn they can intimidate their owners and get their own way. Obviously you want that not to develop. But usually it's a valid form of communicating.
Our current basenji is crabby if you wake her, but using a voice before touching gets an evil look but no growling.
As for training... doesn't matter what you do, the more you work with your dog, the better the relationship, the more they look to you to teach something new and the happier they are. Scent training is really great. I had my child work with our Rottweiler early... the dog bonded with her more than me, and I was fine with that.