You can find similar configuration settings between Messenger and Workchat channels. However, Workchat being a professional, internal-only communication channel, there are some additional options you can play with.
The Broadcast feature allows you to trigger any flow for any given user or list of users. To use the broadcast feature, click on Send broadcast to open a configuration popup.
Under Flow, select the flow you want to trigger
Under Targets, list the emails (one per line) you want to receive the broadcast
Under Context, you can optionally add any additional context that you want to set in the _metadata object for this broadcast
Once you hit Send, the broadcast will be sent immediately.
For a very large number of targets, consider splitting into smaller sets.
If the broadcast were to fail sending for any reason, you would not want to retry all the users again, as some may receive the broadcast twice!