Your first decision is to determine how you want to generate lather. In the beginning it is best to pick a method and stick with it until you can consistently generate a good lather. If you face lather your coffee cup will do. If you want to bowl lather then you can decide if you want the lather warm every time you shave. If you don't want warm lather every time you shave then just get a good lathering bowl. Any bowl can be used, but I have found that larger bowls with some texture are more desirable than say a small cereal bowl as they will generate lather faster and the lather stays in the bowl. Coffee mugs and such are often to small and you end up banging the brush against the walls without generating much lather. Check out DirtyBird pottery for an example of a well designed lathering bowl. If you want to go with a scuttle, get a big one if you are going to generate lather in it. If you are just going to keep the brush warm while face lathering then any size will probably do. Often finding what works for you is just trial and error. Be creative.