I've always written code and text in a very iterative way. Even e-mail I write, re-write and after I make some changes at the bottom I check that my latter statements are not repeating what I've written above.
Now, as I'm writing a popular science book, I'm going about it the same way. There are lots of facts and I am not able to simply write everything down supported only by what I remember and my notes, I still need to go back and double-check the facts. That's something that is wildly different beteween novels and scientific texts I presume. Both will of course need to be consistent, but the former is supported by your ideas and your fiction, the latter is supported by objective data and somewhat subjective theories. And I can't afford to make any mistakes regarding the experimental data, the meta-study probabilities, the references or the quotes, as the critics come down so devastatingly harsh any aspect they can get their hands on.
Half a chapter (on telepathy) is done, I assume progress will be faster once I get the hang of it. And it's still fun! I never liked writing in school, the reason might have been that I never needed to write convincing.
