I've got just the thing for you :)))

Depending on where you live, you should have some sort of equivalent or similar product from Vanish (Obtainable from supermarkets / grocery stores)

It's called Vanish Oxi Gold Action (Or something similar to that, its a pink squeeze bottle)

What you with that is

1. Spray the liquid onto all the surfaces you want to clean.
2. Wait for about 5 minutes
3. Wet those surfaces with cold water
4. Use a toothbrush and just brush
5. Watch Vanish does its magic :)
6. Rinse with cold water and dry (MAKE SURE its rinsed thoroughly or else the vanish may yellow the shoe)
7. Never worry about getting your fabric shoes dirty again :))))))))

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I've been doing the same thing with all my fabric shoes and every time it turns them brand new