Check out this video to see how quick and easy it really is to power level your friend's new character all the way to 60!
You do not have to have a Leoric's Signet. You do not need to hunt down a Cain's set. You do not even need to bother trolling the auction house for various bonus experience items, or any other items for that matter. Watch the video to see proof of how easy this can really be.