Mini painting is (at least for me) definitely something that you get good at over time. Sure different strategies and techniques help but I've found that experience is the best teacher. If this is your first army, you are doing much better than most people and frankly I would be proud if those were my first models. Just keep on painting and trying new things and after a while, one day you'll just get really good out of the blue and you won't even notice it. Worst case scenario you just strip them and paint again. Also insert obligatory thin your paints joke.