Finally, I’ll add finishing touches and make some slight adjustments.
 Overall color adjustment
To create a sense of unity throughout the illustration, I create an [Overlay] layer filled with blue, lower the opacity to about 10% and place it at the top of the layers.
I also create another [Tone Curve] layer to make the whole piece slightly darker and add a little blue.
I decided to increase the saturation a little, so I’ll make another tonal correction layer above that.
I select the [Layer] menu > [New Correction Layer] > [Hue/Saturation/Luminosity].
I gradually adjust the hue, saturation, and luminosity while looking at the illustration.
When I’ve finished, I click OK.
 Details & adjustments
Finally, I’ll adjust some details that are bothering me.
I’ll adjust some parts by cutting and pasting, so I flatten the image to make it easier to edit.
Note: First, I make sure to save a copy of the data just in case.
I’ll create new layers on top to adjust the details.
As I paint, I’ll also edit some parts by copying and pasting.
■ 1. Adjusting the eyes
I want to adjust the direction of the gaze of the character on the left, so I select the irises with the [Polyline] tool and copy and paste the enclosed area.
I move the pasted area with the [Move layer] tool, then paint around the border of the part I just moved.
I’ll also adjust the eyelids. I select this part with the [Polyline] tool and copy and paste the enclosed area like with the irises.
To change the shape of the pasted area, I select [Edit] menu > [Transform] > [Mesh Transformation].
A mesh grid appears over the selected part. I move the intersections of the grid to adjust the shape of the selection.
Once I’ve finished, I press the Enter key to confirm the changes.
After transforming the shape, I use the “No color mixing (blur)” brush that I set up in part 1 to make it blend in.
▲ Before and after transforming the eyelid
▼ Part 1 is here.
■ 2. Adjusting the cup
I want to change the angle of the cup lids, so I copy and paste these and transform using the [Edit] menu > [Transform] > [Free Transform].
Unlike the mesh transformation tool, this method creates a rectangle around the selected area. I drag the squares on the transform rectangle to adjust the shape.
I repeat this step a few times to adjust the cup lids in detail.
■ 3. Moving the characters
The composition felt slightly lopsided to the left, so I encircle the characters with the [Polyline] tool, then copy and paste the selection and move the characters to the right with the move tool.
I make a new layer and use brush tools to add the parts of the background that were hidden by the characters.
■ 4. Painting details on small objects
I felt that the food in the foreground was lacking detail, so I create a new [Multiply] layer to paint some patterns on the hamburger packaging and other details.
When necessary, I create another [Normal] layer on top of this to blend the color in.
I repeat the process of selecting, copying, and transforming any other parts that bother me and adding some final small details, then I’m done.