hey i have another way you can add that i used to do and it worked
1.the host will not get the xp.
2.everyone get one kill.
3.the host will have to leave then the next then the next and so on...(last person will not get the xp)
4.once you backed out prestige and go online get one kill then sign out and you will be level 50 when you sign back in but just prestige again.
this is one of the most efective ways that used to work for me so i hope it helps
*note:this was for the 2+million xp patch*