This is how you do it. Mix water and washing-up liquid. Soak shoes in water, but not too much, after all, it's leather we're dealing with here. Scrub shoes with a toothbrush or nailbrush. An eraser works wonders with spots.
Steel wool is also excellent stuff.
Let shoes dry on a steel hanger. If you stuff them with newspapers they won't loose their beautiful shape. If you are desperate Some spots are just too difficult. Sometimes your sneakers look like new. Sometimes they look dead.