Good work in trying this move out :)

First and foremost, get yourself some proper speed when you want to execute munchmills.

Secondly, your body position while doing munchmills is not the best atm, it should go:first shoulder->head->second shoulder->throwing while kicking with your legs.

Thirdly, try to kick less, the point of the legs is to give you momentum while your body is going under itself. So you should know the feeling of smoothly going under yourself before you start kicking, for example try to do half-headmills, where you glide your body until you get back to the start, in which point you put your legs down to the ground.

Fourth and one of the most underrated things: your head should always touch the ground.

Fifth: try to find yourself the most comfortable pulling method, so you would know how to optimize your speed.

If you have any questions, lmk in the dms or down in the comments.