One of the biggest mistakes when using Gua sha is to neglect your non-dominant hand. For me, that means my left hand. My right hand uses the tool and I'm paying attention to the force and depth of the tool as it glides over the skin. But I actually I pay far more attention to my left hand. The one with nothing in it and the one which is often dangling at people's sides or supporting them as they lean over.
With Gua sha, you have to think in 3D. The skin is just one of the tissue plains and you have to be aware of where you are both directionally and depth. This means that your eyes and ears become your hand which is probing, smoothing, spreading and exploring the area you are applying Gua sha.
Here's a video of me (I live in a forest in case it isn't obvious from the surroundings), showing you how I do it.
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