Incidentally, what exactly makes a person already be a rationalist in this case?
Pretty much someone who has read the Lesswrong sequences. Otherwise, someone who is unusually well read in the right places (cognitive science, especially biases; books like Good and Real and Causality), and demonstrates that they have actually internalized those ideas and their implications.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.