A friend of mine from college had been working there for a very long time and I never even knew it. There's no turnover to speak of so when someone did finally quit in order to move to another state, she recommended me for the job. I grilled her about everything they did and had to know and then made an entire portfolio tailored to the exact job. My friend also secretly brought her boss to look at my work in an art show, so he could see me "in the wild." Thank God, I was nice to him and spoke freely and confidently about what I do, without knowing it was a test. Realistically I probably prepped a good month or so for my interview, going so far as to teach myself a couple of new techniques, and so on. They later said they picked me because my portfolio exactly fit the work they needed me to do.
Now, you won't always be lucky enough to know someone on the inside and grill them about EXACTLY what the job entails and have them vouch for your character, but I can't emphasize enough how important it is to learn everything you can about the job first and completely tailor your resume/portfolio/etc to that company if it's a really specialized job like that where a bunch of people are trying for it. I don't think most jobs are worth that level of effort to try and attain, but this one was.