Blacks are purple-blues, in varying degrees of chroma and to some extent value. It’s easy to see why mixing a PB into yellow will give you mud! The key is to hold the right hue and chroma as you bring the values down to their lowest. Since all the great painters could do this without Munsell it is obviously possible to do it now. Munsell is just the easiest way to get there.
That being said, there are ways to make it work easily without using Munsell. First I need to tell you about the way our eyes work. We can see just over 1,000 gradations whether looking at two values or a complete value scale. This is important because it tells us that the wider the HVC presented in any piece the LESS a viewer is able to see of any component part. Knowing this gives us the ability to create more convincing illusions.
There are only a few really dark colors: ultramarine, peryline crimson, etc. Perhaps one or two for each basic hue. So if I have to bring the crease in flesh down to V<1 I will find the darkest paint that is in the YR range, and add it to black, usually a 1:1 ratio works. The same with everything else. The choices at that value range are so limited that you can fudge successfully with a little thought and planning. I use lamp black for most of my mixes.
Of course, if your lights are not in balance with your darks the form won’t read correctly. But that’s another issue, and one where Munsell really does help.