Automate add followers from custom field value

We currently have a field in our work intake form for submitters to indicate Interested Parties for a ticket. Our team members would take that information and manually add those people as Followers to the ticket. This doesn't happen very consistently.

I would like for the tickets to automatically add the names listed in "Interested Parties" as Followers to the ticket so they are notified of changes and updates.

I've created a new custom field called "Interested Parties" with the data type of "People." I then created a test form with an "Assignee" field mapped to the "Interested Parties" custom field. I did a test submission and this part works: the names I entered into the interested party field map to the correct custom field.

However, I don't see an option in Automation where I can pull the names from that custom field and add them as followers. I would be fine if I could pull their names and @mention them in the comments field.

Perhaps I'm going about this the wrong way? Is there a solution to what I'm trying to accomplish? Thanks.