Ok, the process and practices were simple.
- clop a letter size of color photo using a set of "L-shape" cloppers to find an interesting composition.
- put a tracing paper on top of the photo and block shapes in 3 or 4 value ranges. The first picture above shows it. We mostly used a marker pen (Prisma) for this process.
- mix 4 values with titanium white and black acrylic paint (dries much faster) [mixed the 5th value later] and paint the composition you clopped. The left photo in the second picture shows it.
- reduced the values down to two (black and white only) and paint the same composition. The right photo shows this.