For myself, Step 3 seems to be the hangup (to date). Sure, I have my novel envisioned (more or less) in 5 sentences, which is basically the story told from the lead character's POV, since the novel is first-person. But to tell that same story in 5 sentences from the point of view of each of my other characters? Characters who may or may not be present during every significant scene? I eventually got paragraphs of some sort done for everyone, but with very a substantial amount of overlap. In other words, the paragraphs are really boring and not very insightful.
Then I had an idea. Why not do a timeline or a grid explaining what happens during each major plot point that the main character goes through?
That...actually led to a repeat of the overlap problem!
So out of sheer boredom and desperation, I ended up writing what major thing a character does or experiences in each major segment of the novel. Once I had one segment written out, I realized that if, read in the right order, it sounded almost like a story. So I numbered the events in order before proceeding to the next major plot point. While the end got cramped and muddled, I got the first 3/4 figured out more solidly than I'd anticipated, and even figured out the ending. It also helps greatly if you want characters to have parallel or mirrored journeys.
Don't look TOO closely if you don't want spoiled, but otherwise, thank you, cell phone camera and sloppy handwriting!
So the more I think about it, the more I doubt its usefulness in any story that's not clearly anchored by one main character. But once I was done I was able to go and fix some of those weak "5-sentence character journey" paragraphs to be...somewhat less weak. If I find it helps me long-term, I'll try plotting out a well-known story and post it up here at some point.
Still, it's also quite possible that the real lesson was that if you're stuck, try something different...or just sit there bored until your subconscious works it out. Me, when I see little blank squares I just want to fill them in, but a blank sheet of paper is more intimidating.