@Wretched ...I was going to say definitely not in my case, but... well, I do have to know part of what my character is going to do or say or have something specific that amuses me metawise to respond to part of things or I can't get started. But... beyond that, I often don't know where else it's going until it does. And I very definitely do the cut-and-paste frankenstein pose writing thing. Often the thing I started with ends up in the middle, or I get hit with what the end of the pose should be before I've written most of what comes in between... I usually have a blank file open in notepad++ to paste bits that get cut from a pose into so I can (I hope) use them in the next pose or later in the scene because they didn't really fit right in the one I wrote them in.
Sometimes I also get lost between paragraphs and have to go reread various parts of poses, or I have to go look up synonyms because I know what I want to say but the right word won't come on its own and my brain refuses to use the similar-but-not-right one.
I'm good on the spelling and (mostly) the proofreading and usually catch the redundancies, though. I'm also a pretty slow writer/poser. This fact is not unrelated to any of the rest of this post.