First you will need:
2 Controllers
PSN that is Master Prestige
Call of Duty Black Ops II (PS3)
A PS3
A Brain

1.Sign into the account you want to copy the stats from.
2.Sign in with the 2nd controller as guest account
3.Hit x on the 2nd control at the same time as hitting o on the first controller till you black screen.
4.Whilst it is going to black screen keep spamming x then find the account you want to copy your stats to.
5.Sign in on account you want to copy stats to
6.Wait to connect to online services.
7.It should show the account of the 2nd PSN (One you want to copy stats to) If it doesn't repeat steps 1-6 If it does do step 8.
8.Play a game on the account your signed into (You don't have to play the full game just go in and back out)
9.After you have played the game and are back at the main multiplayer menu press o and it will ask if you want to sign out of your sub account select yes and press x.
10.Go sign in on the 2nd account on the actual Console account to see if it has worked.
11.Enjoy!