How to set up your server Create a private server in any round and once you're on a map open your console (if you don't know how to there are guides on how to do this) and type the following commands:
This will setup your next map to be a wingman game, then type the following:
map [name of the map]
As all maps used on the wingman game mode are the maps used in demolotion mode, if you type de_ a list with all maps on demolition mode and competitive mode will appear, just pick the one you want.
The only one that is missing is Rialto (probably has a different name and doesn't start with de, idk).
And you're set, the map will load with the wingman game mode.
During the warm up you should have 8k $ instead of the 16k $ from the comp.
Feel free to mod the server as you see fit.
edit: To play Rialto it's gd_rialto, thanks to NRK for pointing it out in the comments.
The Common Denominator game mode This is how I and my friends chose to play this game mode.
Create a server with 3 other friends.
Choose a map to play in.
Play the game 3 times, with a different team mate each time, so everyone played 1 game with everyone exactly once.
Keep track of who won each map and at the end tally it up.
It should look something like this:
player 1: W W L
player 2: W L W
player 3: L L L
Player 4: L W W
In this game player 3 is awarded the title of common denominator and will hold it until a new game is played.
Everyone is now entitled to call this player by his title until it is lost.
The other possibility is:
player 1: W W W
player 2: W L L
player 3: L W L
Player 4: L L W
In this case player 1 is the common denominator, but now in a positive note and again will hold the title until the next game.
This player now holds the bragging rights until a new game is played.
Other ways to play this game is each player chooses a map and a team mate, this way 4 matches are played and there is the possibility no one is the common denominator.
Have fun and try as hard as you can to not lose all 3.