Any type of release that does not contain solvents (which may damage the foam) should work. This could be a wax or something like Vaseline, which is what I would use.
If you want a smooth or rigid surface on the foam you could coat it with epoxy as Justin suggested, then use any release you like prior to molding.
Comments
If you want a smooth or rigid surface on the foam you could coat it with epoxy as Justin suggested, then use any release you like prior to molding.
/Chris