Thumbs up on the kneeling in snow advice. Tried doing that while I was teaching a friend this past weekend and it loosened me up so I could extend more. Literally everytime I was posted on the snow, on my knees waiting for her to catch up, I'd be twisted around, grabbing method, with my back hand up imagining myself in the air: hold that for ten seconds, then twist back around the other way, stretch as far as possible, then repeat the whole process.
Took it to the park and it felt a lot better/natural.
Also, the slow mo intro of this vid shows the better way of meloning first, then tweaking method: Learn How To Snowboard: Grabs | Snowboard Tricks For Freestyle Snowboarding - YouTube