Stop the bleeding by sticking the nail into a bar of soap.
I only ever used the cutter for one dog, and that was our PointerX, Bandit...she stood perfectly still...but loved to eat the little clippings from the floor.
I've always used a mini dremel on the Dobes, GSD and the Greyhounds. It's battery powered and light weight.
The key is to keep the battery well charged, and don't let the sandpaper get worn down.
Nixon starts the GSOD as soon as I approach him with it, and I've never ever hit the quick.
He just likes to hear himself scream.
Once I start trimming, he usually shuts up and is very good about it.