There is no actual way to provide a return international postage label so you'll have to send them money via paypal to cover cost of return shipping. Before or after is up to....? Another seller might be able to give you better advice on the how-to's of that. If you send the return postage money beforehand, maybe the buyer just keeps it and your item in lieu of returning it? If you wait until after you have the item back to refund full cost of the purchase PLUS return shipping, it might annoy the buyer.
I suppose it depends on how the discussions between the two of you have gone to date.
