The basic process is to colour the basic shapes in first using a flat colour, for example the skin, armour, hair, wings and cloak were all made different, flat colours. Shadows are painted on next, then midtones, and then finally highlights.
I paint into the flat shapes using mostly hard brushes, it looks really rough at first, and sometimes the flat colour even changes if I don't like it.
Use a few layers to separate the shapes so you can cleanly shade them. Also use several layers for your flat colours and your shadows, midtones and highlights.
Form is painted on with two or more colours within the same hue. Shadows are mostly flat shapes which are cut along the form using an eraser.
Hair is soft, so it gets a hard brushing initially, but then I go over it with an eraser with opacity set to pen pressure.
Drapery is similar, except there is more attention given to the edges using a hard eraser, and then some blending using the smudge tool (be very careful with this tool, it can easily ruin your work). Try to think of the form of the drapery when you smudge.
Wings are also similar to the drapery, except it is a harder surface, and because these wings are more metallic, they need a hard eraser for the shadow.
Skin tones aren't difficult. Begin with any colour (skin can theoretically be any colour, it is highly reflective). Then gradually build up a light tone, your brush must have opacity set to pen pressure, and you gently brush in tones. Don't go crazy with it though, skin has very subtle gradations.
Highlights for everything are painted with a highly desaturated and high value of the hue, close to white but not quite. Use mostly a hard brush, with opacity set to pen pressure.
Shadow, in this case, because it's manga, is painted mostly with a hard brush, and then erased back with hard eraser.
I always brush along the form, and then when blending (with smudge or a regular brush and sampled colour), emphasise the other direction by brushing against the form.