And BMX I don't know about Bennett but I use a weight in the center of the disc during the dyeing to get all the way to the edge. The Buzzz below needed a shot glass about 3/4 full, most drivers just need the shot glass.
My experience is that the disc alone is usually enough to get _to_ the edge - as in looking at it straight from the front it is covered. But if you want to go around the edge, like on Dans Buzzz, you need some weight on it.