The final result is quite realistic with the reflections, I like it!

If you're painting, have you tried Verve Painter as the painting software? (If I remember correctly, its developer Taron is one of the devs for Zbrush.) It's free and has fully controllable fluid and drying and canvas simulation for the paint. This gives enormous color abstraction. And that with very little work. The only minus right now is that it's a beta and has limited undos for high resolution.