I didn't use anything to seal the paint and it stayed durable and bright long after the shoes were unwearable (ripped soles.) Make sure you get fabric paint, since regular paints will be less weather resistant.
I invite you to my new Customizers Forum [link] I have set it up yesterday, it would be great if you could share there your experiences. It would be cool to have some posts there before i make it puplic
Canvas shoes are literally shoes made out of canvas. Not the whole shoe, but the tops. So in this shoe, the part that's covered by my painting was canvas. And of course, canvas is a great material to paint on, so that's why a lot of artists choose to customize this particular type of shoe.