Play over 5,000 Ranked Multiplayer Matches.
I got tired of micromanaging 8-man sessions very quickly. I found that we encountered tons of Xbox Live errors, which prevented stats from properly recording. I also found that managing logistics for 7 other people, both before and during sessions, was incredibly stressful. The amount of time saved by eliminating the 2-minute countdown timer was easily lost just from the clumsy nature of the sessions. Luckily, there's another effective way of doing it that's easy, almost error-free, and requires very little attention.1v1 Quickie Tourneys
This method is mindless, simple, and ultimately almost as effective as using 8 people. A single round of a Tourney only requires 2 players to start and 2 kills to finish, which makes them far superior to Deathmatches or CTFs. You simply need to set up Ranked Quickie Tourney matches with 1 other person (or a second box). There are a small handful of levels, each being pretty small. All you have to do is pick a spot on each map to meet your partner and have them kill you (or vice versa) twice. DO NOT bring a 3rd player into the mix, as it will add multiple rounds to each Tourney match; they are tournaments, after all.
You'll want both players to dashboard every 20-30 minutes, to be safe. If you don't, you may start to run into the problem of having stats not properly record. Also, if you receive the dreaded "Xbox Live Has Encountered An Error" message, you will both have to dashboard as well. These are the perfect type of sessions for watching movies or starting a new series on Netflix, Amazon, or Hulu and just zoning out. It requires very little concentration. Depending on how fast you are, you will hit anywhere from 18-30 games played in a 2 hour session. Slow, but that's Quake 4 for ya.