Man this is so simple- You don't have to worry about non friends joining the lobby all you do is ( for Cod4 or Cod waw ) is get 7 people in your party. Then go to Ground War- Right as everyone disappears off your screen you Back out ( O then up then X (or B up then A)
THIS IS THE HARD PART- you quickly open up the playlist and select domination.
If you weren't already in a room and you did this while it was finding a room it should redirect to domination bringing your whole party of 7 with you.
Finally you log out and back in. Then you get one person to leave, and go to single player and back. Then one of your friends invites him back. Then your friends invite the rest of yours/their friends to fill up the lobby and there you go.