After I'd completed the basic sketches, I copied all three layers and merged them, then decreased the opacity from the layer properties and created new layer.
In this layer I went for more detailing on his face, eyes and hair through different kinds of pencil shadings. You can see examples of all the strokes I used in Fig.06 - 08.
I knew that eyes and the mouth area are very important when it comes to portraits or caricatures, so I worked hard on those particular areas. Now my sketching part was finish and I could move on to adding colors.
After I'd completed my sketching part, I copied all the layers and merged everything into a single layer. Then I selected Multiply from the Layer properties options menu of the "sketch" layer. I did this because by using the Multiply option I could see my drawing and decide whether it was going accordingly or not when I painted in color. For coloring, I always prefer the brushes shown in Fig.09 (Hard Round airbrush and Pen Opacity Flow airbrush).
I opened a new layer under the sketch layer and started to roughly paint in the shape of the face using a darker or medium color for the head. It's important to choose the appropriate color at this stage because the base color will lead to add more detailing later.
Then I used darker tones on his eyes, mouth and lower face. On the third stage, I used darker tones, as shown in the circled area, according to the source of light (Fig.10).
I also compared my image with the reference photo and found that it was coming along okay. I also checked it further with a horizontal flip. It's a good practice to check the sketch or painting by doing a horizontal flip to allow you to check for any volumetric distortion (Fig.11 - 12).