There's something relaxing in making such kind of illustrations. More observation, less geometrical thinking. On the other hand accuracy is crucial. Every millimeter plays a large role as it can change someone's facial features beyond recognition.
But there is even a bigger problem with portraying an actual person. It's an anxiety about the reaction of a model. Supposingly the vast majority of people are particularly sensitive regarding their appearance. I know that from my own experience. Yep... it's time for a short personal digression:
Over ten years ago my parents commissioned an artist to make a pastel portrait of me. When I saw results I was, to put it mildly, disappointed by the way I was presented, or maybe perceived? The approbation from the family didn't make my mood better (I would say the contrary). How could they praise that? The girl on the portrait looked completely different from my own self-image. In my (presumably biased) opinion she actually didn't look like a girl, but like a not-so-pretty, emaciated boy. It took several years before I admitted to myself, that maybe... just maybe... I looked... just a tiny little bit... like a not-so-cute boy back then. Anyway, since then I have a very cautious approach to the subject of portraits.
Now let's get back to Patrick- an owner of Elly Guitar Company (what a luck that he have a healthy approach to the subject :D ). Illustration below is a part of Elly's guitars series http://www.grimdreamart.blogspot.com/2015/01/handmade-guitars.html and is meant to be used as a background for telling the company's story.
1. Pencil sketch - rather delicate as it's meant to be a base for watercolors.
2. Watercolor background and subtle sepia shadows. At this point I'll explain the process of making such a "weathered" paper. We use a broad brush to wet the whole sheet with plenty of clear water. Then we place a very diluted watercolor paint with the same broad brush (I used few shades of brown and yellow here). We need to move the paper in various directions for quite a long time to allow the paint flow in the way we want. Of course the final effect is more unpredictable than well planned, but it's possible to influence it intentionally to some extent. Here and there (but rather not everywhere) we can place a pinch of salt or splash denser paint. Sometimes we can use a paper towel to wipe excess diluted paint. I noticed that results are more convenience if the edges are more "interesting" than the central part.
3. I admit that I was struggling for a quite long time with Patrick's nose :D
4. Additional elements. As this drawing is a sort of continuation of guitar schematics series, it require a similar frame. I also pasted a schematic of one of these guitars (digital technique can be so useful sometimes :) )
5. There's only left to add a text about Elly history in the blank space!