Thank you guys. Actually I have used only two brushes during the painting of this figure. A Raphael number 1 and a number 2.
The Raphael number 1 has a belly twice as big as the W&N 7 serie number 1. So you have twice more hair which are able to hold more paint and more importantly more water in order to slow the drying of the tip. For freehand work, I never dilute my paint that much. Most of the time, it is one drop of water for one drop of Vallejo model color paint. I like also the W&N serie 7 and used them also, depending which one I have on hand on my workbench. I think that you could actually even use a number 3 for doing delicate freehand work as long as the tip is perfect !