ok first of all start mw2 first before starting ur mw2 host tool ( doing this reduces the chance of ur mw2 game crashing becasue of the mw2 host tool) then go to lobby find game like teamdeath match now make sure ur the only in the lobby then copy paste this command in the console and enter it
party_hostmigration 0; party_connecttimeout 1; badhost_endgameifisuck 0
now dont press f5 coz it will disable the search u will have a hard time finding players and the players will have a hard time finding you through the match making system now if you think u have enough players then press f5 to disable searching then u can now press f4 for the game settings and if done editing the game settings you can now press f3 to start the game, then ingame while plasying u can press f5 to enable searching, after the game when in lobby again u can press f5 again and then f4 for the game setting and f3 to start the game