Hello. Those wishing to participate in the signature company need to keep an eye on the free slots in the spreadsheet or will there be messages responsibly in this thread?
For now the campaign is closed for new participants only the manager of the campaign can open slots if the need be or any member leaves the campaign but still then, the manager has the sole responsibility to open vacancy which would call for applications.
The campaign manager would definitely make announcement on this thread if there is opening for the campaign. I will suggest as you have said to constantly keep an eye on the thread to see when a slots open to be filled up then the manager would make an announcement for application.