Balance is good. Not too much, not too little - the more water you have, the more of a wash effect you'll get. It's true that going over the things with a little dark ink wash to make sure the cracks and crannies all have paint in them helps - it still looks rough, but you don't have those little bright spots sticking out of all the dark armor to advertise that you missed a bit. ^^;
Spraying a clear sealant on them (I prefer a matte, myself. iirc, Testors makes one. I don't know what might be available in your area, I use what I have which is, don't laugh, called 'Mr. Super Clear'.) is a good idea - helps keep the wear from normal handling down.
No guns needed, this is an aerosol can; but you will definitely want to do your spraying outdoors.
They'll look better as you keep doing it. And I suspect that, as you get better, people who don't/can't paint will start begging you to paint for them, which means you will get more practice, on different minis than you might ordinarily buy.
You can charge monies for this (and if you don't want them to take you and all the time and effort you put into learning for granted, you totally /should/ charge for it, but that's a different rant), and thus fund your habit. It turns into a bit of a cycle. <.<