Now comes the fun part, the COLOURING! :D
I always start with the skin colour as it is mostly the lightest area on a picture and you won't run into trouble with dark colours e.g. the marker picks up some of the dark colour and smears it all over.
Rule: Always work from light to dark!
Ok, in order to achieve the gradual fade from the base skin colour I used the Blender 0. Since the Blender does not include any colour, in fact it's totally colourless, you don't need to worry if you go over the outlines if there isn't any bordering colour.
First I "coloured" the skin area with the Blender until it looked wet. Then I used E00 to create the fading effect by leaving out parts that were supposed to be white and built up the colour from there as you can see in the little image. Sometimes I had to go over the coloured part again to make it darker. For this step I needed to work fast so that the colour does not to dry.
It's good to do one part of the skin at a time (marker colours