Saddle soap on a damp sponge to work up a lather then a soft shoe brush to get into the stitches.

I do not endorse any products, this is only to show you what I'm talking about 😊

https://www.amazon.com/TAKAVU-Horsehair-Shoe-Shine-Brush/dp/B077K8PR8P/ref=mp_s_a_1_5?crid=1D9KJG1REYMKT&keywords=soft+shoe+brush&qid=1685909444&refinements=p_85%3A2470955011&rnid=2470954011&rps=1&sprefix=soft+shoe%2Caps%2C124&sr=8-5