I’ve been using this “technique” for a while now, and all I can say is that it had a HUGE (positive!) impact on our sex life and I can only recommend it. We both don’t masturbate in private anymore and learned (yes, learned!) to do it out in the open, next to each other. That requires trust, you have to open up on your feelings, communicate. Plus I find it sexy when my partner does it, and I often join in as you’ve written. Or I don’t when I’m not in the mood. It was a life changer for us!