Any Suggestions Would Be Appreciated

I am looking for suggestions on cutting dogs nails, specifically a dog that is difficult and will not let you touch her feet. Andy and I have had Madison for almost a year now and we have never been able to cut her nails, so you can imagine how long they are. They are so long now that they are lethal weapons. Every time she jumps on me I feel her stabbing me in the side and it is painful. Andy and I have asked around for suggestions and I feel we have tried everything. We took her to PetSmart at least a dozen times and asked them to do it for us and every time they came back saying they were unable to do it. These are trained dog people so if they can’t even cut her nails then how are we suppose to? We were also suggested to use an electric sander. Andy has a small hand held sander looking thing that he thought would work, but of course the noise scared her more than anything, so that didn’t work. We also read online to give your dog Benadryl as that will knock them out and then we should be able to get those claws cut, but of course that hasn’t worked yet either. We have tried this approach a few times and so far I haven’t seen Benadryl knock this terror out at all. So, you see what we are up against? If you have any suggestions on getting these claws cut before she stabs me one more time please let us know. I am ready to try anything if it means no more abuse from the dog!