"Just One Nail" started years again when I had 4 Consults in a row that all needed help with the dog attacking during nail trims. They had varying degrees of fearful responses with the last being a Springer Spaniel (we'll call him Jack) that had to be full sedated at the vet for a simple nail trim! By the time I got to Jack, I had found a pattern and asked the owner what happens if they trim just one nail. He never tried just one so he did it, Jack was tense but the first nail was a bit of a surprise and caught Jack off guard. The owner decided to try another, also fine but when he went to trim the 3rd I stopped him as Jack was clearly building his rage.
The idea is simple, by trimming just one nail and following it up with their meal you set a pattern that you work on every day, a pattern that your dog can predict and will begin to look forward to instead of running. In fact, a month into doing Just One clients report that their dog beats them to the drawer holding the Clippers
You don't need to do Just One forever. This works because it keeps your dog under threshold and is just a starting point to getting your dog comfortable with the process.