The CMYK skin-tone method is best used as a guide for correcting skin color, not as a literal white-balance replacement.

A common rule of thumb from the community answer is:

• Yellow should be at least equal to magenta.
• For lighter skin, yellow is often about 5–20% higher than magenta.
• For darker skin, yellow and magenta are usually very close.
• Cyan should be roughly 30–50% of the magenta value.

In practice, you would sample a representative skin area in Photoshop and use Curves or other color adjustments to nudge the channels until the sampled CMYK values fall closer to those relationships. This is useful because skin is not neutral gray, so a gray-dropper on skin itself is not appropriate.

So: use a neutral target or gray card for actual white balance when available, and use CMYK skin ratios afterward as a visual/technical check for pleasing skin tones. Photoshop is the typical tool for this workflow because it gives you detailed sampling and curve controls.