Poach all your eggs as normal, but under-cook them slightly. A minute off of your normal cooking time should do the trick. Just make sure the whites are nearly set. Strain the eggs and put them into a refrigerator container filled with cold water.
When you're ready to serve, bring a pot of water to a gentle simmer and give your eggs their final minute of poaching. Because the whites are already set, you can heat several eggs at once without worrying that they will stick together. This takes much less time than poaching all the eggs at the last minute - and it's less stressful, too!
We usually poach the eggs the night before or the morning of the brunch. If it's already close to serving time, you can also hold fully poached eggs in a bowl of warm water so you can do several batches of eggs but then serve them all at once.
Do you have any other tips when poaching eggs for a crowd?
Related: Eggs Benedict and Beyond