I have noticed that when i actually mew properly its always in a natural and relaxed way. I normally mew by making my molars lightly touch then i start to mew and swallow with my tongue. After spending a a few weeks paying good attention to my mouth posture then contrasting that with today in which i didnt focus on it all I noticed I mewed better or atleast i feel like i did. When relaxed my jaw would hang a little open when i had to swallow my jaw closed like it did when i focused on mewing more but it was slightly different I could just tell it just naturally put me in the "BUTTERFLY  BITE" As Mike Mew talks about. My teeth were in much lighter contact then when i did it manually and there was a stronger suction on my palette even though i was applying zero to little force. 

The main gist of this tip is the put yourself in a natural position to swallow properly dont even really think about it. Just think about swallowing and the tongue doing the work. dont focus on it like crazy to swallow properly I find i almost never feel like i get good tongue posture when i do that. be relaxed in your face and pretty much  the only thought should be dont let anything BUT the tongue do the swallowing.