OK, so a lot of people are having trouble with this, First you're going to need 6 people, best way to do it, next you're going to want to download UDP unicorn, its a lag switch, its the easiest way to get in a non dedicated server.
So
Step 1. Make a SnD custom game with unlimited lives and time and save it, then publish it by clicking your name and going to showcase and then click custom games and publish it.
Step 2. Get your 5 friends in your lobby.
Step 3. Find a match of SnD, right after you start searching click attack on UDP unicorn, put the target on 27.27.27.27, and the port on rand, I have the delay on 20 and the packet size at 45 and it seems to work pretty good.
Step 4.you should be in an empty lobby with you and your 5 friends, at the top right there will be a server number if there's no e at the end then it worked.
Step 5. Everyone INCLUDING the host load the custom game the host saved.
Step 6. Everyone vote for the same map.
Step 7. Once it picks the map you wanted, load the custom game the host saved once more.
Step 8. Sit and wait for randoms to join, your done.
ALSO, THE GAME ENDS IF THE BOMB IS PLANTED, SO SPAWN TRAP, KD DOSENT COUNT BUT XP,HEADSHOTS, ECT. DOES. once you're done, either plant the bomb or let them plant it. The just load out of the game and repeat steps 5-7 unless people left then step 8 too.