Painting skin tones don't have to be complicated. Using a limited palette of a yellow (quin gold), a red (quin magenta) and a blue (Prussian) can create beautiful vibrant clean skin tones. After you complete your sketch, start with wetting your paper until the shine is off and then take a med. wash of yellow and touch your paper. Use the wetness of the paper to assist in letting your colors flow. Keep the edges against the white highlights clean and soft. I don't use masking fluid anymore, for the tiny highlights, I will come back in at the end of the process with a white pen and add them back in.