This step is mostly reading and thinking, with a little cut and paste thrown in for fun.
First, read over the rough draft of the scene you did in Step 3. Do your best to ignore the clunkiness of the language (remember, we're not worrying about making it sound good yet), and focus on structure and flow. Anything need to be shifted around? Does it feel like there's a missing paragraph somewhere? Fix that now.
Then, open up your first draft version of the scene, and at long last, read it. If you do not immediately notice that the new version is better in all ways except sentence flow and word choice, then this whole process is probably not for you. But the first draft probably has a lot of good stuff in it, too-- stuff you want to salvage and use. So copy and paste any lines or passages that make you say, "Damn, that's good. I forgot I wrote that."
Again, this is a quick step. Probably not more than half an hour.