The last time I did that, I just put the paint right on the shoes: stripes, spirals, dots, graphic designs. I also used a toothbrush and stick to get neat spatter effects. The cheaper the shoes, the better. Then I hung all sorts of crazy charms from the shoelaces. I wish I still had those shoes; I wore them out but haven't gotten round to painting another pair yet.

Those little squeezy tubes of fabric paint (Tulip, etc.) work nice, too, because you can get a raised effect and since the tubes have narrow tips, you get a lot of control.

I never bother putting any sort of sealer or topcoat over the paint, because the acrylic bonds to the canvas well enough. Acrylic works great on fabric, too. I also have done T-shirts with acrylic paint and they can even go into the washing machine, if you turn them inside out first, and line dry them. Again, I didn't bother with topcoat or heat-sealing or anything. Just painted it and let it dry.