im not going to go into a huge tutorial because there are plenty out there, but if you want you can make your 1v1 into a bigger lobbie.

1. Make a party with the people you want to boost with
2. Have two people do the initial glitch, but when the host dashboards after going into theater and backing out have all the other party members dashboard as well and sit at the multiplayer screen.
3. Now the playercard person just hits A, A, B and presses Y and goes over to party and invites the party.
4. Wait until everybody is in the lobbie. Hover over wagermatch and pess A, A, A fast just like usual. and it should let you guys go into the Demolition just like usual.