I only M&S my entire head after washing it, and my sections are always at least 8 (max 12). When I do less I end up with too much hair in the middle and throughout the sections with no coverage. I do like to separate my sections in halves to detangle, so my Denman can glide easier and I remove more shed hair that way too.
When I M&S daily I just do the sides, top and bottom. I'm transitioning so I do not touch the length once it's already set.