1. Sketch/Lines with base color
2. Use a soft edge airbrush to add some reds, pinks, and purples to the folds.
3. Blend in the colors with the base skin tone.
- You can add little specs of light to make it look wet or shiny
- Using red and pink for the armpits help the eyes move to them if that's the main focus.
- Keep in mind how lighting would affect it if you have a hard time with skin tones. It's pretty unrealistic to for light to affect it too much.