When I watch the class, I thought for me it is more fun to find other ways to use this technique. I think all kinds of line art are suited to use. With Procreate I imitated the technique in three different ways. 

1. The bottles I did with two layers, showed in the class. My first drawing: the bottles.

2. I changed the technique.  I started with dark layer with some texture. Above this layer a layer with a line drawing. Above the line drawing a layer with colors.  This layer was set in clipping mask. So the lines of the drawing are colored above the dark layer. (The fish and portrait)

For the rooster I changed the technique:

3. A dark layer, under the line drawing of the rooster and a empty clipping mask layer above the line drawing layer. Clipping mask is on. When coloring in  the clipping mask layer, you see only  colored lines of the drawing. So you can decides were to put the colors.

T3:

T1: 

T2:

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T2.

 

T1