If the plant has several good roots, I wouldn't go the sphag and bag method, I would repot them into whatever mix he/she is using, and then be diligent in watering them. If G Thumbs wants, he/she could put a loose tent of plastic over the plant for a week or so, just until the plant gets adjusted into it's new pot. By the way, don't overpot as that's an invitation to rot as there will be too much medium that can stay wet in compariston to the root system. Use a pot only as big as the root system with just a bit more room for growth.