I start off with a very simple and rough sketch using the pencil tool. For this part, I try to pay attention to proportions and anatomy but not focusing too much on detail just yet. This gives me the "skeleton" for the line art.

The sketch opacity is reduced and a new layer is added. We'll call this Layer 2. This will be the layer for the body, facial features and objects. Here's when I do corrections for the posture, shape and position of the subjects in the drawing.

Then on another layer (Layer 3), I draw the accessories, hair and other details (cutie mark in this case). I added a speech bubble for Lotus saying welcome in Japanese because why not?   When I'm finally satisfied with the finished line art, I can clear the "skeleton" layer.

As I'm using the free version of SketchBook, I have access to only three layers per drawing. So to make room for two more layers, I merge both Layer 2 and Layer 3 together. Now I paint the base colour on the former "skeleton" layer which is below the line art layer. At this point, I want to experiment with the colour shades since I'm not using any original show references, thus the out-of-line colouring as shown below.

After selecting the right colours, I start colouring in properly and using an eraser clear up the mess outside the lines. I then start shading the eyes using the fine airbrush tool and adding highlights to them with the fine paintbrush tool.

Once I'm done, I create another layer for the shading the body, eyelids and the accessories.

Keep in mind: I am only allowed a maximum of three layers. When the shading so far is satisfactory, the shading layer will be merged together with the base colour layer.

Now for the hair shading. On a new layer, I use a both the pencil tool and the fine paintbrush tool. I began by painting with shades darker than the base colour before moving on to white highlights. Once that's done, this layer is merged together with the coloured layer.

For the final background layer, I will need to make the colour layer invisible. This will allow me to see the full background as it is with no obstructions but at the same time lets me see where I need to paint the counter.

With the wide airbrush tool, I begin with the base colour and followed by the shading. For the writing on the counter, I used the pencil tool and added the shadows with the fine airbrush tool. To make it look like it's behind a glass panel, I used the wide airbrush tool with a low opacity setting and sprayed on white lines.

...and that's all to it I guess.