hey :-)

Its simple.
I tell it in MY steps how i do it:

1. Find someone that has the prestige that you want.
2. Go on the lower account that you want the prestige on and go to multiplayer > Public Match > Add second controller > Click with 2nd controller on Store.
3. It will give you an error and then with your first controller press Circle (O) > And with your 2nd controller press (X) like at the same time you press circle(O) with your 1st controller.
4. It will sign out your account.
5. Click fast on Public Match it will ask you to pick an account.
6. Pick the high prestige ( or whatever prestige you want)
7. Sign in and go to public match and then just press circle. It will ask you if you sure to sign out your subaccount, click on Yes.
8. It will give an error and press Public Match again and sign in with your lower account you want the prestige on and its done.

Goodluck, if you have an 8th prestige to borrow for me i can give you an 11t(master prestige) or 12th prestige accoutn in return.

-Remco.