I think shoulder flexibility has been the one thing I've found the hardest. I've been working on just trying to get a haircutter spin all year and I am at the point where I can grab my blade in the spin (either from a layback or just reaching down from an upright spin, but that's it.. I can't pull it where it needs to go while I'm spinning.
For now, work on getting full splits, work on laybacks (you can even do that off ice), and work on being able to reach and grab the outside of your blade with your palm facing up (you arm will be twisted) so that you can pull it up behind you (into a haricutter) with your elbow pointing at the ceiling. From THAT position is where you pull up into a Beillmann.