It’s Thursday, so it’s Q&A day…
For this task it’s best to just use a graphics tablet and a mouse. Add a new layer and trace over the photo with a low-opacity brush. Duplicate the layer and draw all other details, such as hair and eyes, on top. Next, duplicate the same layer again, use a mouse to draw the thicker strands of the hair and then a tablet to draw the finer ones.
Now merge all the layers using Cmd/Ctrl+Shift+Opt/Alt+E and reduce the Opacity. Apply the skin colour, shadows and hair tone by sampling as you go, then merging them via Opt/Alt and the Brush tool. The trick is to use the Colour Balance, Hue/Saturation and Selective Colour adjustments – along with blend modes – to create an artistic pattern. To finish, sharpen the image by going to Sharpen>Unsharp Mask to make the painting look authentic.