When ever I needed to roll up a skein/hank of yarn after dyeing it or from Purewool, I had to find something (or someone) to hold my yarn. I tried several different methods before I found the one that works the best...
the car seat handle!
It is the right size to fit the skeins of Purewool and if I prop it up against the footstool, I don't have to work too hard to get it to unwind.
Of course, a REAL swift would be even easier and I'm still hoping to make one, but in the meantime, this gets the job done!
Sitting next to the yarn in the seat of the carseat, is my "ball winder". I first wrap the yarn around a book a few times, then I slide it off and "sandwich" it between the handles of two flat wooden spatulas. Then I wind the yarn around the handles to make the ball. When I'm done with the ball, I pull the spatulas out one at a time. And Presto, a center pull ball!