Preparations before applying the base color
I painted the base colors separating the layers for each part.
Creating a layer folder for each helps to manage the different parts of the image!
■1. Creating layer folders
You can create a [Layer Folder] by dragging and dropping the separate drawing layers onto the [New Layer Folder] icon in the command bar of the [Layer] palette.
I put all seven of the created parts into layer folders this time. Considering that different parts may overlap with others, it may also be helpful to change the order of these layer folders.
The [Layer folders] have the same names as the contained layers.
■2. Creating layers to paint the base colors
I placed each layer meant for the base colors below the respective sketch layer in its layer folder.
 Painting the base color for each part
I painted each base color using the colors from the “Palette” layer.
As a sub tool to use when painting the base colors, I recommend a pen with even paint.
This time I used the [Pen] tool’s [G pen], but the choice of pen or brush depends on the person, so there is no problem using your favorite sub tool.
To roughly apply the colors, I chose a large brush size.
As shown in the image below, I painted the base color for each part with reference to the sketch.
[POINT] What are pens and brushes with even paint?
Brushes with the [Mix ground color] function deactivated, while nothing is set for [Opacity - Effect Source settings] in the [Tool Property] palette, usually don’t produce uneven paint.
In the initially available sub tools, the [Pen] tool’s [G-pen] and the [Marker]’s [Fill-in-mono pen] are suitable for painting base colors.
 Finalizing the outlines of the parts
Once the base color of each part was painted, I painted the outlines of each part more firmly.
Working carefully here makes the subsequent process easier. Let’s carefully paint while referencing the sketch.
Since this will be the base for the above painting, make sure there are no gaps left in the end.
Once everything is painted and has no more empty spaces, the base as such is complete!