Welcome! Great that you can shave with your grandfather's razor!!

Everyone develops their own technique and preferences about where to build a lather ... heck, some people do it right on their faces! If you get a soap, you may be (like me) using a combo of the soap container and your face. For creams ... you need somewhere to lather. Your size of brush may dictate that in part (bigger brushes may not work well in a mug; bowl only ... smaller brushes anywhere).

I lather with room temperature water, so I'm not part of the crew who go to all sorts of lengths to keep their lather warm ... the scuttle is one of those options ... but you may really enjoy the warmth of the lather, so to each his own.

Enjoy the shave!!