The TDM method proposed by Failure Online
yields the fastest number kills/per match versus VIP, but here is an improvement on that solution.
If you can get a session for six people, then the host can create a match using the following settings:
Minimum to start: 6
Score limit: 50
Time limit: 10minutes
At the beginning of the session, propose pairing up with another and make sure to get on opposing teams.
Once the match starts, one person and his/her pair on the opposite team run to the other side of the canyon and spawn kill the other two people on the opposing team. If one team reaches 49 first stop and let the other team get to 49. Whoever needs the win can get the last kill which will go towards the Laurel Wreath achievement.
This method will give two people 49/50 kills about every ten minutes or less. What takes the longest time is making sure your partner gets on the opposite team and the possibility of dealing with randoms as TDM is more popular than VIP.
If there are any questions, clarifications on the solution, or or reasons for a negative vote please post in comments so I can improve on it.