It is not easy to paint a human face because it is not easy to paint a human being. Personally, I estimate that every twenty-fifth or twenty-sixth attempt of mine is a total failure. It can be discouraging to have every attempt come out looking like something somebody has left the canvas beside a dumpster or is trying to get a quarter for it at an estate sale. When I get very overwhelmed about the challenge of painting a person I take a breath, paint a couple of dogs or a hamster, and try again. You could do a shrub or a car as well.
Broken down, a portrait is nothing more than a skull with some skin and cartilage, some protrusions and indentations, areas of shadow and light, flatness and protrusions. But, if you just painted those things then you would have nothing more than a painting of anatomy. We want to create a painting of a person with a soul, not a skull with some features sticking to it.
There are other challenges beyond trying to capture the heart and soul of a person. The human skull is such a bizarre shape and if painted incorrectly (i.e. with the eyes on the top of the skull instead of dead center in the skull where they belong) your portrait will resemble a side character in a Despicable Me spin-off. When you break us down to our bits and parts we humans are slightly ridiculous looking with our huge foreheads and deep-set, gloomy eye sockets that are really two, dark gouges in our face. Nostrils are bizarre, our skin tone is generally some kind of strange color like months-old silly putty and our ears look like bizarre appendages escaping the sides of our heads. So how do you paint what you see when what you see is a little strange?
That is all why painting portraits is so hard and why I had concerns about trying to teach a portrait painting class during Painting 101. What can intro level painters do with a portrait? Painting a portrait with some soul is challenging even for people with years of painting experience under their belt. So, when teaching people to paint people. I returned to what I always return to: Paint what you see, not what you think you should paint. Don't paint what you think an ear looks like, look at the ear of the person you are drawing and depict the exact lines, the shadows. Paint the parts exactly as you see them and don't worry about the whole.
I have, on occasion, tried to make life easier by removing the face entirely and doing a portrait based on the spirit of the person. By focusing on a recognizable outfit, hair, a gesture, a way of walking or dancing of a person you can actually do a lovely portrait. Who we are is recognized by others in many different ways.
You can capture the spirit by focusing on the elements the most remind you of them. In the portrait below of my grandma (who I call Crazy Grandma Marie, as opposed to my other grandma Marie who was sane). It is a brief sketch of her taken from a photo of her in her era of being a new bride. I wanted to capture the nerves of a young, sheltered girl facing life as a wife and a mother so I focused on recreating her pose, which was tentative and scared. And since, even as her massive breasts collapsed into some sort of second stomach that rested over her original one, one grandma liked to brag about the beautiful figure she had when she was young, I made sure the curves were there. And the face, which I feel captures both her as I knew her and the image of the nervous bride from the photo, is nothing more than 3 dark marks (two eyes, an (uncertain) mouth) and two different smudges of skin tone to define the highlighted portions of her face. I was fast and purposely sparse with marks and color and I think it captures her perfectly.
One bit of advice that I think is on display in this image it to try to get the mouth right because that reveals so much about a person. I focused on the mouth and the eyes in the following portraits of my niece Tessa and my daughter August as well. I didn't worry about getting skin tone perfect, or getting their features identical to what they look like. I focused on the spirit of them, which in my opinion is captured when you focus on the mouth and the eyes.
Good luck. Have a lot of paper or canvas on hand for the inevitable failures. And if it all goes wrong turn that painting of your husband into a shrub and start again.