I tested this a couple of times, and searched the forums. No one mentioned this so I thought I would post it. Feel free to test
1. You and your low level buddy form a group (LvL 80 must not be in group)
2. Que for LFD
3. Upon joing the PUG LFD convince or wait 14 minutes for some one to either leave or get kicked from the PUG LFD
4. Invite via your friend, list your lvl 80 friend to "TELEPORT" in the instance to via the dungeon button to start clearing for fast xp.
5. Rinse Repeat