Or try thisI think I found the right tongue posture--I spread my tongue and suction it, I feel a nice relaxation and the soft area under my chin rises like the guys in the videos. Only problem is I have to hold my breath 100%. The back of the tongue has to be up for it to work, but I just can't breathe.
1 - create the suction in your mouth
2 - try to tuck your head in backwards while still maintaining the suction (think of it as a turtle trying to get back in its shell) - you should feel your back neck muscles react strongly when you do this
3 - once you feel your back neck muscles flexing - lower your lower jaw a little while still keeping your mouth closed - you should feel MUCH easier to breathe throughout the nose while still easy to maintain the suction