Regarding the mug and cake, you've got two options. Option one is to put the cake in the bottom of a mug and make your lather in that mug. I did it that way for over twenty years before I discovered option two. Option two is better but it requires two mugs, or containers or of some sort. You load lather onto the brush using the mug with the cake and then you build the lather in the second mug. This way is better because you have better control of varying the ratio of soap and water when building the lather. For more info, see the wiki!