Mewing, by having correct oral, tounge, and Neck Posture, and Strongly Pushing Up and Forward with Your Entire Tounge on the Roof of the Mouth/ Palate is good too, and can be most of the day. The tounge is the Strongest Muscle, and probably the best anchor, as well as a light force throughout the day.
Probably the best thing and most important thing to do, along with Face Pulling, and Neuro-Cranial Restructuring.
Neymahr seems like a scam artist, trying to get $4000 for a a Generic Email full of unproven information.