I've got about 6 or so soaps on hand.
I almost always use these 2.
My favorite is tallow based, Lather&Wood Bay Rum, that comes in a metal tin.
Proraso green in tube is very refreshing but not tallow based.
I use very hot (microwaved) water to soak brush in.
I use a soap mixing bowl for the Proraso
I use just the wet brush on the tallow based.