It doesn't take much for a dog, and a rottie in particular, to form a negative opinion about something. And clipping nails seems to top a lot of dogs lists. I don't think i have anything to add except the treats and the desensitizing to a dremel. I've also noticed that I had a tendency to squeeze their paw while i was trying to squeeze the nail clippers, hence switching to a dremel. And it's harder to nip the quick with a dremel. Good luck!