https://www.youtube.com/watch?v=FhWSuyLkqVI

The only part I disagree with him on is how long you can hardmew for, personally I can only 100% mew for several minutes, but I can hardmew with a medium force for the whole day, except when I'm sleeping. I also disagree with him on suction hold, using force with the tongue is actually more crucial if you want a suction hold, you need force to get the tongue as close to the palate as possible to get a strong suction. His theory that it retrains that hardmewing retrains the muscle memory is correct in my experience, I've been hard mewing the whole week every waking hour and when I'm not thinking or conscious about it I'll catch myself still mewing but with a light force, I've even been able to fall asleep while mewing with a light force. So I think hardmewing as a conscious exercise you do every time you're aware is extremely useful if not crucial. I used to get pain which is why I didn't hard mew, but I ramped up to it and I no longer get pain, only a strong pressure. You should also try your best to get the tongue inside of the arch, push against the alveolar bone and not the teeth to the best of your ability, it's impossible to not touch the back teeth but you can definitely avoid the front teeth which is more important because the front teeth are weaker.