I had never done it before just lately. Doing it for the 9mm. Here's mine:
You can't see it, but there is a steel bar (about quarter inch) running across the middle/top of the bucket that the cotton (T-shirt) is clipped to.
Here's some of the result:
Interesting process. It actually speeds up my casting as there is no messing about with the boolit after it leaves the mould, it falls and you refill it.
Cat