I saw the comments on that video before watching and thought "It can't be that bad can it?" Afterwards, I honestly wouldn't recommend doing that UNLESS you are a beginner. It just comes out... sloppy.
The top comment, at least on my web page when looking at the video states this (removing the backlash): "...when it comes to black highlights as has been pointed out blues, purples, are great to mix with your black paint that still makes it look black but with a very subtle shade. Mixing black with a brown leather also makes for a subtle variation for belts, straps, shoes etc. You can have a totally back miniature that still looks 3 dimensional without using super harsh contrasts like you have done here..."
I'd follow this, but if you really, REALLY, want to keep it without a sort of black with a shimmer of grey for the highlighting, use black and just make it the darkest grey possible you know? So like 2 parts black, .05 parts grey.
The idea that the top comment states, from youtube, is that there is different types of materials out there, such as midnight blue (A good example would be
this but the darker area in the upper right) or other colors.
Again, not to downplay the posted video since Jay does fantastic tutorial vids, it's just not something you really want to follow since it's done... well badly.
EDIT: Greyguy13 which model of commissar is it anyway?