For some people, especially very talented artists who have been doing it a long time, drawing the face of a human is easy and fat... for the rest of us it can be extremely complicated or even frustrating. I have been involved with art for most of my life and I still find it very difficult so I always take my time and go slowly. Even with a pencil instead of paint or pens, this can be a very time consuming process.
My process isn't complicated, I just start out lightly so that I can made eraser adjustments if needed, then I gradually fill it in as I go along.
The eyes and the various wrinkles that exist on all faces is something that takes a long time to master, and some people like me, it isn't something that you ever truly master. It still takes me a lot of time and patience to get these things the way that I want it to look, but in the end normally it ends up paying off.
In the end, and you can probably tell by the differences between the two photos, I ended up abandoning the hair altogether. The details on hair can be extremely difficult as well and all you have to do is look at famous animations to realize that what I am saying is true. Even famous studios like Disney when they were hand drawing films and Pixar using computers, decide to go with "block hair" rather than having flowing hair most of the time because it is extremely time consuming. Just think about how many individual strands of hair you have on your head right now.
Also, and I have mentioned this many times before, when doing full scenes I almost never focus on realism in the faces of the participants in whatever scene I am doing. For me and most other artists the time it takes to get it right and especially if the faces are small, it can be more trouble than it is worth.
I'm quite happy with my end result here and although it should disappoint me, I'm actually quite pleased to say that several of my students have already gotten perhaps a bit better at this than I am. It actually makes a teacher proud when a student takes the information that you have given them and then uses them so well that they actually get better at it than the teacher. This shows that they are absorbing the knowledge and perhaps a genuine gift for the craft.
Enjoy your art lives!