to share individual contacts with QR Code between two devices, a slim (700kb) qrcode app will make this possible:
Despite its ability to scan qrcodes, it will add the ability to generate a vcard QR Code from the Contacts share menu, and will also detect a vCard text after scanning one to be imported into Contacts
(I had less luck with other open source qrcode apps, that in other regards are excellent, using this app was the most straightforward way)