To-date, it's not a job anyone can "get". We decide amongst ourselves who to approach, then go from there.
I'm considering in the future making it not only an open-application process, but submitting all candidates to community vote. The vote likely wouldn't make the decision but would be influential. Especially the Yes/No ratio of each candidate. I would want people to simply tell whether they'd object to each person; not vote Yes for their favorite and No on the rest.
Assuming we need any more Admins. I think we're going to need 2 more in the coming 6 months, but wouldn't mind being proven wrong. Once there are enough Admins to really stay on top of the workload, the workload, by definition, should start going down in some respects. I hope.