I work on a concept in stages - usually starting with a charcoal/graphite sketch and then moving onto a digital study/painting. The final step is in physical media. Sometimes this process is in reverse or goes back and forth between media.

Bronze Face v3 (Charcoal/Oil/Digital)
highfalls (Oil on Paper)
solstice (Oil on Paper)
Golden Speckle Girl
Introscopic Landscape 1 (Oil/Digital Study)