Out of country BnP etiquette

[Festafarian]

I do a lot of BnPs and I have a question about the best way to do a BnP that's outside the country. Usually, I tell people to send a sase, but, I cant mail a package from the US with (for instance) Austrailian stamps. The last person to request a BnP from me suggested sending a couple of extra blanks to cover postage, which is fine with me. I don't want cash involved, but I'm not sure if this violates the "2 for 1" restriction, plus I don't really think that the blanks cover the cost either, since postage will probably be $3 or $4. U2Lynne suggested using international postage vouchers. I did this once, but because I live way out in the country, my local post office had no idea what it was. I ended up driving to the city to use it (which cost more in gas than it was worth) Any ideas on the best way to handle this?
Thanks

[hanshak2015]

You could collect the international vouchers and use regular stamps for the outgoing shows, then cash in the vouchers some time when you drive into town anyway. Not an expert though, just a theoretical idea.

[Festafarian]

Good idea, may be the best way to go
Thanks