Summary: you will probably get good and consistent results if you store your puck of Williams to keep it moist, pasty, and soft. No fancy brush is required. If you have a small tupperwear container to hold your Williams, you're all set.
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After building some decent (I thought) lather with a two different brushes (and taking a lot of photos of the process), I realized that the way I'm storing my Williams never gives it a chance to dry out. I keep it in a Tupperwear container with the lid closely tightly. Maybe this has the same end result as soaking the puck in water over nightówith less to do?
The puck never gets dry and always has a sort of soft, pasty surface. I didn't intend for that to happen, but that's what did happen. If you're able to load the brush with a decent amount of soap, more than half the battle is over.
So it likely has nothing to do with the brush. This time I used a Plisson and a good old Rooney 3/1 with super silvertip. I realize for some a Rooney may be fancy brush, but it's not stratospherically priced, and AFAICT, is a popular choice.
Here are two sets of thumbnails linked to larger images. Both show the pile of lather and the brush that created it, followed by your 'humble narrator squeezing the brush and showing the lather on his hand.
First, the Rooney 3/1:
Now the Plisson:
Although I haven't directly compared, I'd say the lather isn't a moist or cushion-y as MWF or Cade or Haslinger or any number of other soaps. It's also nowhere near as expensive as the soaps I mentioned. But my experience so far indicates that, once lathered up decently, it's a serviceable soap that can give you a DFS. YMMV, of course, but that's my experience so far.
Unrepentant Member, P.O.G