We have found a few different options to be helpful, especially with virtual events:
Share the materials and group assignments in advance, so that participants can take time to prepare and develop ideas to share.
Encourage active participation during the event itself by asking for different speakers each time.
During the debrief for virtual events, we find it useful to break out people into private groups of 2-3 people (if your web platform has this feature). This helps discussion flow more easily and prevents only a few people speaking up about their experience in the larger main group.
Use the 60 seconds of silence after closing the summit or creating a successful En-ROADS scenario. We find that this gives time for participants to process the experience and be able to sit with how they're feeling, something introverts might crave after a high energy simulation.
Assign participants a follow-up writing assignment (such as this exercise for En-ROADS or this exercise for C-ROADS). This can help those who weren't able to participate as actively, or who take a longer time to process, to share their thoughts.
For more facilitation techniques check out: