Create a ranked game and get your partner to join. alternate killing each other or if they already have/you're using a dummy account you can kill every time.
Assuming a rate of 1 win and 1 kill per minute with a boosting partner who doesn't need the achievements (or a dummy account) this will take ~84 hours.
Converting the minutes to hours: 5000min/60min = 83.33h
If you can get it down to 45 (3/4 or 0.75 of 1 minute) seconds per match/kill it will take ~62.5 hours. Multiply by two if both players need this.
Converting minutes to hours: 5000min*0.75 = 3750min/60min = 62.5h
While doing this you will also get 5000 kills.
This is easily one of the most time consuming achievements I've seen.