And my try to explain what I did each step...no guarantee for completeness, correct spelling/grammar and comprehensibility though
Layers are always named from the bottom upwards, meaning the first layer mentioned is at the very bottom of the stack, percentages behind layer names refer to opacity
1
layers: white background, base colours, lines (100%)
tools used: standard brush (hardness 100%, size: large-ish, depends on the actual size of the pic in question)
Filling in the base colours of the image, already establishing basic shading
2
layers: white background, base colours, lines (50%)
tools used: blur
Smudging the base colours to erase the harsh boundaries, already keeping the shape and direction of the texture in mind
3
layers: white background, base colours, lines (50%)
tools used: standard brush (hardness 100%, size: medium)
Adding the lightest and darkest colours to get more contrast
4
layers: white background, base colours, lines (0%)
tools used: blur
Repeat step 2 and remove the lines to see if the outlines are more or less smooth
5
layers: white background, base colours, lines (10%), details colour, horn, eye
tools used: standard brush (hardness 100%, size: 1 to 3 px)
Start adding details to the shading with a small brush, mainly roughly filling in the light and dark areas that will differentiate the structure of the face, using the lines of the sketch as orientation on where to place the main characteristics like the eye, nostril and horn. Those things should be placed on a seperate layer so that one does not accidentally paint over them later on.
6
layers: white background, base colours, lines (10%), wings, details colour, base mane, details mane, horn, eye
tools used: mane: standard brush (hardness 100%, size: medium to small), wings: standard brush (hardness 0%, size: medium)
Adding the base colour for the mane and establishing a basic shading for it. Adding rough detail to the wings with a soft brush (keeping them blurry as they are not the main focus of the pic)
7
layers: white background, base colours, lines (0%), wings, details colour, base mane, details mane, reflex mane ( 30%), horn, eye
tools used: details mane: standard brush (hardness 100%, size: 1 px), reflex mane: standard brush (hardness 100%, size: 5 px), blur
Adding detail to the mane by using the lightest and darkest colours, defining the direction the different strands have with the length and direction of the lines.
Adding pure white reflexes to the mane, similar to the ones placed on the body in step 3 but on a different layer; using blur to soften the edges and set opacity down to about 30%
8
layers: white background, base colours, lines (0%), wings, details colour, base mane, details mane, reflex mane ( 30%), horn, eye
tools used: blur
Using blur on the colour details, again keeping the shape and texture of the face in mind
9
layers: white background, base colours, lines (0%), wings, details colour, base mane, details mane, reflex mane ( 30%), horn, eye
tools used: blur
Blurring the details on the neck and body, adding proper shading to the horn
10
layers: white background, base colours, lines (0%), wings, details colour, base mane, details mane, reflex mane ( 30%), horn, eye
tools: standard brush (hardness 0%, size: medium)
Some last touch ups to fill in some missed spot in the colour details, add a few additional shades here and there and softening the transition between mane and neck