Zbrush spotlight - let's talk about texture quality

Fist of all, my workflow: I sculpt my highpoly model in Zbrush, then I polypaint it with the realistic textures (via spotlight), then I export HP model to xnormal where I bake "Highpoly Vertex Colors" into diffuse map. My lowpoly model is of course properly uv mapped.

Now the question: Did any of you guys find a way how to paint a crisp and high quality textures in Zbrush? My experience is that even with very dense mesh (a lot of subdivisions) after baking my diffuse map lose a lot of texture quality and overall impression is very smudgy. It is too bad that final texture quality depends on polycount of polypainted model. Any workaround or tips on that subject? Maybe one word - MARI?


By the way -- little math question for you : Imagine you're working on a wooden barrel for a game. Your "working texture" (which is loaded in Zb's spotlight) is 4K. Your final diffuse map have resolution of 2048x2048. My question is: how many active points in Zbrush should the model of barrel have if you want to produce (= bake to lowpoly) VERY DETAILED and not smudgy diffuse texture (again it's 2048x2048 ) ? I'm talking about top notch AAA game production quality output Thanks