The washing would depend on the type and brand of paint you choose, but, typically, once you paint them they are pieces of art, and aren't really functional as everyday shoes.
Once you paint TOMS shoes, they aren't meant to be washed or cleaned beyond dusting them when they are on your shelf.
Here is a link to the "How To Have Your Own 'Style Your Sole Party'" website:
... on that page there is a link to download a checklist that has all the paints, markers sewing stuff, etc... that they suggest for making your shoes into art.
If you have further questions after reading that page, then
You can contact TOMS by clicking here to call their style your soles hot-line or e-mail the styles person:
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