Coloring the base colors and shadows of liquid
Next is the bottle on the character’s waist.
① First, the liquid inside the bottle is painted. After a new Layer is made and clipped to the base color layer of the bottle, the base of the liquid is painted with the [Pen] tool → [G-Pen].
② A yellow gradient is added to the base color with the [Airbrush] tool → [Soft].
By using an unusual tint, the liquid feels like a magical potion.
③ After creating a new layer and setting its blending mode to [Linear burn], shadows are drawn on the bottom of the bottle.
 Adding highlights
① White is used for the highlights. A new layer is made, and its blending mode is set to [Glow dodge]. Highlights are drawn with the [G-pen], and are blurred and blended with [Soft].
② Another new layer is created, and weak highlights and strong highlights are layered. The highlights are painted while considering the clearness of the bottle.
③ Finally, as the bottle is transparent, the clothes showing through the bottle have to be expressed.
The deep purple of the clothes are added, and the bottle is finished.