I haven't used that type of scuttle before, but I imagine its not too different from other scuttles.
I believe you simply put a cake of soap on the top bowl and fill it with hot water through the "spout." Then, put the brush in the "spout" to warm it up. To lather, work up a lather on the soap, and the excess water drains down into the scuttle.
I'm curious how well these works. I haven't seen anything written about them. But, since T&H, C&E and others put out the design, I have to imagine they work pretty well.
“A shave, please, but don't cut my throat. I may want to do it later myself.”
- Casey Stengel