How would you pick Tespia participants?

What you do is hold registrations (like KMST) for those who WANT to participate in Tespia. Then you have those who register, on their applications, explain in full detail why they want to participate and how efficiently they would search for and report bugs. Then you proceed to pick the top applicants from the list to be your testers.

It's a more work-heavy process, but it would definitely turn out better than choosing people randomly, who probably don't even want anything to do with a test server.

kMST doesn't have registrations. It's a "pick me pick me -pulls random people from hat-" sort of thing, afaik.