I third that advice. When I think about it, I wonder about that I use a combination of both the arm and the wrist sometimes. I don't think too much about it. As the people say, just do what is comfortable.

You know, I was like that before, was very worried about whether I held my pick the 'right way' or not. Then I just forgot about it and focused on playing, and whoa, now I don't think about it anymore. Same with pinch harmonics, palm muting, everything really. Just experiment.