First you invite them into the party chat and game

Tell them to edit playercard hover over layer 1

When they are tell them not press anything unless you tell them so

Now get into a search and destroy lobby not game (lobby)

It will say you need to switch to game chat

Ok now you press no

It will boot you to player match lobby

Now tell the other person to say no

Then you invite him to your playermatch lobby

Then you tell them to say no