Getting into the pose I shift my weight towards the leg in half lotus pose. This has the consequence that my the one sitting bone doesn't remain on the floor anymore. Moving my body in that direction makes it possible to wrap the leg. I've to twist as much as possible. It also takes several breath till I'm deep enough in that position, but it's doable. My hand can hold the wrist. I used to move the weight back, so that my sitting bones were on the floor as soon as I've bound. When I do this the leg that is in lotus pose goes up and is somewhere in the air.
From a youtube video by Kino MacGregor I learned that one doesn't move the weight back. The one side of the body is up, but it will come down with time. For me it makes more sense to let the gravity work and to let the body move downwards from alone than to try to force the knee to the floor.
Another advantage from not moving the weight back is that the shoulders remain parallel.
Pictures: My right side seems to be a bit better.
Currently I also work on the correct breathing. No additional breaths. The correct vinyasa count is also part of the Ashtanga practice.
PS: I've started a photography blog. Have a look and feel free to like it.