Aaron's method is based on three cornerstones: knowledge, time, and enthusiasm.
By knowledge, Aaron means you should know what you're going to write before you write it. This doesn't just mean outlining in the usual sense that most writers use, but even something so simple (as she mentions) as sitting down for five minutes before your daily writing session and jotting down notes on how you want your scene to go.
I am an outliner--I outline at the chapter level because I find it almost impossible to finish stories that don't have some level of preexisting structure. (I learned this the hard way, after leaving dead story-corpses all over my hard drive and not being able to finish things for years. There's a reason my short story output per year is not great.) I rarely outline in more depth than that because I have almost never found it helpful to do so. Well, in a spirit of open-mindedness, I tried Aaron's method while working on Dragon Pearl. I spent about five minutes and worked out where I thought the scene was going to go. Within 500 words, I had gone completely off the rails, so that was pretty much a waste of time. I could have tried it again, but I know myself well enough to be pretty convinced that going off the rails would be a regular occurrence. I mean, I'm the person who tossed off Kel formation instinct almost as a throwaway worldbuilding detail only to have to practically take over the trilogy (it's a major theme and plot factor in both Raven Stratagem and Revenant Gun), and a character who had not even existed in the outline for Revenant Gun ended up becoming one of the major secondary characters. So, uh, yeah. Since I'm prone to zig where I was supposed to zag, this bit of advice is not helpful to me. But it might work for you.
By time Aaron means time management--not just making the time to write, but figuring out your own writing output patterns and playing to your strengths. So if you take a couple weeks to record your wordcount output and discover that you write fastest in the evenings, then prioritize writing in the evenings. If you write best when you have several uninterrupted hours, try to arrange your life to make that possible. Things like that. This part I'm pretty comfortable with. I don't work another day job--I'm a stay-at-home parent. I can pretty much arrange my hours however I want. I'm not great at time management, but this is more a function of my terrible willpower than lack of self-knowledge.
The last bit is enthusiasm, by which she means that stuff you're genuinely enthusiastic about writing will go faster--often much faster--than stuff you're not. I have experienced this; I think many of us have. Unfortunately, this doesn't really help me. I am sitting on a weapons-grade mood disorder. My being able to sustain enthusiasm about ANYTHING for longer than a few hours is pretty much never going to happen. When I have writing projects scheduled out a couple years in advance, it's pretty hard to imagine being able to maintain any level of enthusiasm for the work to come. And, I mean, besides bipolar disorder being disruptive, I spend a lot of time depressed, including depressed about my writing. So this is just a wash.
She does have one useful insight that I've observed about my own writing (and which I wish someone had told me rather earlier), which is that when you seem "stuck" in your writing, sometimes it's because your subconscious is trying to tell you that there's a glitch in what you're currently trying to do, and you need to reconsider your approach. I have definitely had that experience--generally once I figure out a solution to the problem in the writing, the "blocked" feeling resolves itself.
Anyway, the Rachel Aarons of the world may well be able to write a decent novel draft in the twelve days that she cites, but I am never going to be able to do that. I can't sustain much more than 2,000-2,500 words per day without burning out, partly because I don't think fast, partly because writing is a painful endeavor for me. I guess I will have to be resigned to being slow and suboptimal. Her observation that you should be as excited about your writing as you want your readers to be particularly dismays me, because I spend most of my time hating my professional writing  and by this standard I'm just doomed. :/ But that's not Aaron's problem, it's mine.
 In all fairness, my fanfic isn't much better, it's just that in fanficlandia people tend to not actually leave comments if they think your fic sucks, they just leave crickets. :p