yeah, being that I work at a school, I have used the crayola washable markers. They are good for use with fabric and wash out completely. I have also used the "wet-erase" markers with great success. But you have to be planning to actually wash the item: neither one is very easy to just rinse out of part of the item without washing.
That's brilliant! I have a bunch of wet-erase I use for drawing on vinyl maps for D&D. I'm so glad i won't have to go out and buy something special.