oh, see, you're TRYING freehand, though, and very early in your painting career. You have the potential go go far.
Also, it's tough to get an even coat on a tank with just small brushes - something which you've done pretty well. All you've got to do is add in one tank effect to bring this up a notch. By this I mean put a few VERY thin coats of a dust color on the bottom third of the tank (or do drybrushing) to create a dusty effect (
this is an example of mud, but you get the idea) or make very judicious use of mithril silver to add some dings and scratches (
like this), or you can do
both at the same time.
Either of these techniques would be a relatively easy way to start expanding your skill set. Plus, if you don't like it, you can always just paint blue back over it. No foul.