That's a pretty good first time painting there! I didn't figure out highlighting, or secondary colors, or blending, for years and years. I look at one of the models I painted fifteen years ago and I honestly wonder how it could possibly have actually won an award.
Something that gets tossed around a lot is the idea of thinning your paints. It's very good advice. Some people will tell you to use fancy stuff -- I just use a drop or so of water. The paints last longer, you can control the brush strokes more and they won't show as much, and it's easier to blend if you use lighter layers. It also means you can add more layers of color before the details begin to distort. And it will look a lot smoother, too!
Excellent work on the basing, too! When I'm about ready to base mine I paint the entire base in a light brown color. You can use green, brown, whatever color you think looks best. Keep the lip clean of basing and use it to mark individual units, or paint a name on it. Here's the way I based mine -- you don't need to fill the entire base with grass, and sometimes it almost looks better if you don't.