Flat coloring 1
I moved my two line art layers into a layer folder, and created another layer folder underneath that. Then, I added more layers for each part and added flat colors.
The blending mode of the layer folder with the “line art” and “blurred line art” layers is still set to [Normal], so the [Multiply] mode of the layers only affects other layers in the folder, and doesn’t affect the flat color layers.
I set the layer folder’s blending mode to [Through] so that the layer’s blending modes would behave in the same way as before they were moved into the folder.
As I paint each part separately, I end up with a huge number of layers, so I started with the biggest parts: the foreground, middleground, characters, and background.
I used the [Fill] tool and the [Pen] > [Turnip pen] tool.
I painted with the fill tool for large areas.
However, when painting with the fill tool alone, some parts can get missed because of the angle of the lines. If there were unfilled parts, I went back with the [Fill] > [Paint unfilled area] tool and painted them in.
It cleanly fills in small areas, so it’s very useful.
▼ Unfilled areas are circled in red. With the [Paint unfilled area] tool, these can be filled in with just one stroke.
I painted the detailed sections with the turnip pen tool, as this tool uses solid color. My basic flat colors look like this when finished.
I will adjust the colors at a later stage, but at this point I have divided the area clearly.
 Flat coloring 2
I split the layers that I drew in step 1 into several layer folders, then added more detailed flat colors in these folders.
I created new layers on top of the broadly painted flat color layers and set them to [Clip at Layer Below].
This means I can paint without going out of the flat color area.
Now my flat colors are done.
Once I finished the flat colors, I adjusted the overall tone and focus.
First I applied textures over the entire canvas to add nuance.
Adding texture makes the image look more hand-painted.
I prepared several textures that I had already made.
It’s a good idea to create and save textures that you find easy to use.
In this case, I used five textures.
■ Texture types
Textures 01, 02, 03, and 06 are old paper textures that I bought from a materials website.
07 is a watercolor texture I made myself using the watercolor brush.
I went to the [File] menu > [Import] > [Image] and imported the textures as image layers.
Note: You can also import textures by dragging and dropping the image files directly onto the [Layer] palette.
I carefully adjusted the blending modes and opacities to get the effect I wanted.
I usually prefer to use the following four blending modes:
・ Color burn
Note: For more details on layer blending modes, refer to the following TIPS.
In addition to the textures, I also added one gradient layer to adjust the colors.
I used the [Gradient] tool to create a gradient and adjust the overall colors. Like with the textures, I carefully adjusted the blending mode and opacity to get the effect I wanted.
This was the result once I added the five texture layers and one gradient layer.
 Tonal Correction
After adding the textures, the cohesion of the piece became clear, so I then adjusted the flat colors to settle on the final color focus.
I selected the layers for the colors I wanted to change and went to the [Edit] menu > [Tonal Correction] > [Hue/Saturation/Luminosity] and used the sliders to adjust the colors on each layer.
To create a sense of depth, I made the objects in the foreground darker.
I also made the inside of the bus yellow to look as if the lights are turned on.
Aside from this, I made some tonal adjustments to other minor parts and finalized the colors.