I only have a little experience to share.
Parties are often slow to get started and guys often hesitate to be the first ones to do something. It’s good to either have some pre-designated guys who agree to go first. For example talk to two (or more) guys and ask them to agree to begin with sexual activity in a location where they can be seen once the party starts. That often breaks the ice and other people will then feel less shy about engaging.
A game as dumb as spin-the-bottle can kick things off. Only rather than for kisses, it may be for 90-seconds of oral sex (or whatever).
Having arrive-by, start, and end times helps everyone know what the selections are, make a choice, and do it. There’s a party organizer in New Mexico who throws events where the arrival window is a nude social mixer before the actual sex party begins. Everyone knows what’s available from the beginning. Otherwise, guys will (like you see in bathhouses) wander around looking for someone even better than what they’ve seen so far without engaging. And, they know if they don’t do something before the known end time, it’s not going to happen.