ive found that fingernail polish does not work that good. it chips awa easy pretty easily, and it doesnt seem to lose that odor
i like to paint my poppers with acrylic paint, and then put a thin coat of epoxy over them. it makes them tough, and the float a bit lower in the water. right below halfway up the body.
i make my poppers out of balsa and cork though, it might be different on foam.