You have some skill here, it just needs some refinement. Your basics are there.
Here is the list as I see it (so take that for what its worth):
-In lieu of the heavier layers of paint, try using very thin layers after your basecoat - further instead of trying to get complete coverage in one coat on your basecoat, use 2-3 thinner layers.
- When shading and highlighting try and make the transition a bit smoother by using your base/medium color in the transitioning layers. i.e., If shadow grey is your base color and you want your highlights to be space wolf grey, slowly add the SW grey in successive layers
- Using these thinner layers, always pull your brush to where you want the paint to build - for highlights pull away from the shadows for example
- Keep your brush wet, but unload it. What I mean here is have a paper towel or napkin (Or coffee filter, as they absorb fantastically) to drain off the excess paint. This will prevent pooling and help smooth your transitions. It should dry very quickly as well. If its not drying fast enough, blow on it. Remember to clean your brush often when doing this.
- Your metallics may need some tweaking but I am the wrong person to ask about that as they are my biggest weakness these days.
As I mentioned you have the basics down. Time, patience and practice will bear fruit if you use them.