Just to warn people - I'm a few wins away from this trophy, but it is very annoying to boost. It is easy to initially match up with your partner, and for one of you to throw the game - however, I believe the matchmaking algorithm doesn't want the same people facing each other multiple times. After I face that person once, we haven't been able to find each other again when searching for an opponent. Considering the server is practically empty - I doubt that's the issue. The only solution I can find so far is creating a load of alternate accounts and throwing the games with those with your partner if you want to boost online. Quite annoying.
Edit - You can face the same person, but only on a new day.