I'll just tell you what I do to backsweeten... it's quicker that way,

and everyone who has done it has their preferred method. This is what works for me:
Make up a solution of one part by volume of honey and 3-1/2 parts by volume of water. So, that could be 1 cup of honey mixed into 3-1/2 cups water. This will yield a liquid that has roughly 1.092 SG. Adding exactly one cup of this solution to a 5 gallon batch of mead will raise it's specific gravity by approximately 0.001 (commonly called 1 gravity point). Thus a dry mead at 1.000 SG will be 1.001 SG after the addition of one cup of this solution. I just add this liquid, one cup at a time, to the bulk of my batch until I get to the sweetness that I desire. ;D
NOTE: you are slightly changing the overall volume of must with the addition of each cup, so the cups that you add after the first will each make progressively less than 0.001 change in net gravity, but that difference doesn't amount to much until you exceed, say, 8 cups or so. If you are after a sweet mead to begin with, I'd suggest changing the ratio of honey to water in your addition liquid to get to your final gravity quicker. For example, a ratio of 1 cup honey to 1.75 cups of water will yield a gravity change of 0.002 per cup when added to 5 gallons of bulk must.