Conceptually, painting scales isn’t all that different from any other kind of layering; in fact, it’s very similar to jewelling.  Basically, you’re just building up a range of one color—green, for example—from dark to light, but in a pattern.  There are several ways of doing it, but I personally consider the following to be the best balance between detail and expedience.  There are lots of patterns you can use; round, irregular, “shield” shaped, diamonds, etc.  It’s a matter of taste.  For our example, we’re going to go with green shield-shaped scales.  I’ve put a simple image in with each step to make it a bit easier to follow along.

Well, it's been something like three years ago when I first said I'd do up a tutorial on how to “jewel” your 'Mech's cockpits. I've graduated twice from two different colleges, gotten married, gotten into two new games, painted a bunch of miniatures, and generally done everything you do in three plus years of time since then. But hey, better late than never right? So without further ado, here's my jeweling tutorial for cockpits (and indirectly, laser barrels).