Same as Kurgan, I tend to take a lot of pictures and then write a report alongside them afterwards. This is more convenient than taking notes while playing the battle.
Regarding fluff, I always had a lot of fluff made up for my warband while converting and painting them (I am always thinking about why the models looks the way it does and why the particular fighter would join the warband etc.). It makes reports a lot more fun to read than just account of casualties and who was moving to which position in which turn.
However, you should resolve these issues to your liking. Some people like more text and fluff, other prefer a lot of pictures with little text, etc.