I opened the photo in Paintstorm. I reduced the opacity to 50%, as I will be using it as a guide. I will reduce the photo's opacity to zero when I'm through. On a new layer, I used the Simple Ink pen to draw some outlines. On another new layer, I used the same pen to draw a suggestion of the fringe of his scarf. When I use this pen, I increase the Stabilization in brush settings. That results in Paintstorm smoothing out my strokes so they don't wobble so much with my hand. Then on a new layer, I used Texture Brush 3 (under the pencil icon) to paint some off-white highlights. Then on another layer I painted with the Classic Transparency brush with a soft gray color, to paint some shadows. I blurred the layer to soften the shadows. Then on a layer just above the photo layer, I started to paint in some color with the Watercolor brush. In this image, I still have the opacity of the photo layer at 50%.

After seeing the result, I decided to erase part of the gray shadow layer, just to the lower right of his face. I changed the outline layer, fringe layer and highlights layer to overlay mode. This gives the lines the color of the area they are painted over, rather than a stark black. I painted a touch of color on the mouth on the watercolor layer. I lightened the yellow background layer, and I painted on it with the watercolor brush. Then I opened the image in iColorama. I used Brush/Paint with a blue/gray brush at low opacity to paint over his clothes to darken them a bit, to bring more focus to the face. Then I brightened the image using Effect/Levels.