Putting shine onto a character's hair can give any drawing a little more 3D detail. It is pretty simple, and it can be used in many different ways, no matter which way your character is facing. In this tutorial, I will be using a generic head, from the back, to draw my hair shine onto.
I drew a basic head of hair and added a few different shades to make it a bit more realistic. However, this is simply a sample head that I will be working on.
IMPORTANT - Make sure you do all of the steps below on a separate layer from the layer that you drew the head/hair on, or else you won't be able to do some of the later steps.
The coloring for this can depend on multiple variables. First, what color is your drawing's hair? Second, where is your character? If they are outside, then take the color of your character's hair, make it slightly yellow-er, and then make it lighter. If there are clouds out, make it a bit whiter, and then lighter. If there are in a cozy home, make it oranger and then lighter - The main thing here is to make the color lighter.
First, draw a line straight down the center of your drawing's head, or wherever you are making the shine. Then, in a semi-circle shape, draw other lines, slanting and getting shorter the further back you go. You should have about 5-8 lines total. It's ok if the lines aren't evenly placed from each other, like mine, because in the end, it will make it look more realistic.
This will be the base for the hair shine. Because of the way that hair falls, some parts are lighter and darker when light is shined on it, so these lines will represent brighter areas once we blend them in. I used the Soft Line/Sketch Color brush under the Marker subtool, but you can use any brush you would like. Generally, softer brushes will work better. You can also use the same settings that I did, such as opacity and brush size, for results like mine, but again any soft lines will work.
First layer of shine
After you draw the lines, color over them in a semi-circle that matches the curve of your lines. I would recommend the Soft Airbrush tool for this because it gives a nice soft effect that is easy to blend into the hair in the later steps. Again, you can copy my settings, or use your own for a different look, but a soft brush makes the next steps easier.
Next, you can use either the blur or blend setting to smooth the lines and the airbrush together. I used a little bit of blurring first, then finished with a good amount of blending, but you can do it however you want, as long as you don't make the base lines completely disappear. They are important for giving our hair shine depth, making some parts brighter and others darker. Smudge the lighter part around until it is a gentler fade into the hair, but not too much.
Use the airbrush tool again and draw randomly off of the curve you created in the first three steps. I did an imperfect zigzag shape, to make it look random but not like I tried to get it that way. A zigzag works well here, because of the way the hair naturally falls. You can even try looking at someone else's hair, or your own in a mirror, to see the way the shadows are cast at different angles of light for inspiration. Make sure your airbrush isn't very dense, or it will reverse the blending you did in the last step, or overpower the lines from the first step.
Use a soft eraser to take off some parts of your curve, accentuating the zigzag we created in the last step. Any parts that look fluffy, like in the picture below, should be erased. You can also go over other parts with the color brush to adjust to what you are doing with the eraser.
Re-doing and finishing
After re-doing steps 4-6 a few times this is what I came out with.
You can repeat these steps (Blending, Adding texture, and Erasing) until you get your desired effect. Keep in mind that I used a generic head shape to easily draw this off of, and on a character of your own creation it will look slightly different.
Thank you for going through this with me - I hope it helped!