How do you use the color wheel for mixing paint?

Hi all,

had a question regarding the color wheel.  I mostly do figures, and have kind of guessed when it came to mixing my oil based paint for figures.  I have read Shep's book where he describes the color wheel, but is there a place that describes in detail how to mix the appropriate amounts for specific colors?  It would be so much easier (and take less paint) to be able to look at a chart and mix the exact amounts.  Thanks much!