Timmy
Reference photo. Hm. You know, when they make photos of real people into D&D characters on Baldur's Gate and other games like it, there is much more than just using filters to it and I can accept it is an art. I have tinkered with the style myself, but only as a passing fancy. Nothing at this level.
In essence, 4 to 5 hours sounds about right. I forgot the terminology for this technique though. Although I must criticize it a little.
The angle of the light. The whites are a bit soft and the shadows on "my side of his face" I think should have been deeper and darker. The nose and cap suggests the light source is on the upper right side of the face, since the left cheek isn't highlighted at all, just a neutral skin tone. The shadow behind the ear absolutely should have been darker. The back of the neck, definitely needs to be darker. The nose on the left side could have been a touch darker to show depth and contours as well.
Normally, I like to use multiple light sources to give off interesting shadow and light zones.
Overall, this is well done piece.