I'm not a brilliant player, so killing someone with the Combat Knife and then killing them with their own gun is pretty difficult for me. I've only done it twice, and both times the progress wasn't saved. I will help you if you need anything too. I'll be in a party by myself, and you just need to join my game, and if we are lucky, we'll be on separate teams. I'd call it boosting, but it's the only way for me, as I suck. PM if you're interested