The most important step is to draw the features of the subject and the shape of the head properly. No matter how you master it, just get the right features. One method is to use the box. Place the box on the photo and then draw grid lines on the canvas and just copy what you see to the canvas square by square. You may even be enough talent for freehand drawing. I'll let you in on a secret, but you must keep it for yourself. If you have a photo on your computer, just enlarge it, upside down or mirror image, then trace with tracing paper. Now just place the tracing paper on canvas and reproduce the right image without knowing things about the drawing!.
Now make the skin color and block in the whole skin. Using white, yellow, red, and burnt sienna to create the most skin tones. Obviously adjust the amount of each color depending on the actual color and tone. Cat must be very thin like a watercolor. Using these colors and add some burnt sienna to paint in the line of the nose, eyes and mouth. Make sure that you use a brush, a very fine thin that it will be a thin line.
Now make the skin color and block in the whole skin. Using white, yellow, red, and burnt sienna to create the most skin tones. Obviously adjust the amount of each color depending on the actual color and tone. Cat must be very thin like a watercolor. Using these colors and add some burnt sienna to paint in the line of the nose, eyes and mouth. Make sure that you use a brush, a very fine thin that it will be a thin line.