I believe you are correct. You can keep adding water to the brush, little at a time, as you face lather. You should see the lather continue to build as you add water to the brush, into big happy mounds of lather goodness on your face that won't dry.
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Adding a bit of water to sit on the top of MWF/DR Harris/Tabac soap pucks is another case of YMMV as I never do and still manage a nice lather. You gotta find what works for you.
Bob
Mine is grated and pressed into a little pyrex dish. If I put water on top of the grated soap, it makes the brush pick up little pieces of soap when loading that don't mix up that well. I find wet brush on dry soap works better for grated. I swirl my brush on the soap until I have a thick cream, then transfer to the bowl and add some water.