Looking very nice, Khonner!
My NMM is terrible right now but two things I do know. NMM depends on good blends and contrast. Blending goes hand in hand with thinning your paints. I use Reaper paints a lot. There's no set ratio for dilution because there are so many factors, certain colors can be thinner than others, age of the bottle (even if you just bought it, who knows how long it was sitting in inventory), humidity of the area you're working in...do you have fans going? Live in a swamp and have 110% humidity like I do? lol!
You may want to try thinning your paints gradually. I've always heard about the consistency of skim milk...but...that's an old analogy. Try thinning progressively until you can get the colors a bit more translucent. Go super thin and you'll be doing what's called juicing and that takes uber patience because you can barely see the colors as you apply them. But getting nice blends with highlights and shadows means you don't have to depend on wash to shade your minis. Wash can be good, but layering will give you a lot more control.
Contrast means taking those blends and pushing the highlights and shadows as far as you can. Not an easy thing to do, believe me I know. But, like most things, you just need to keep painting, keep practicing. It won't happen overnight but you'll get there.
Keep up the great work!