by Nekau
From what I've seen on the pictures the cogs looks easy enough to drybrush.For those of you not familiar with the technique, its best described as the opposite of washing. If you use a wash, you let the paint sink into the small holes on the cog. When drybrushing, you use a larger brush, put paint on it and then stroke most of it away before applying it the cog. The paint then sticks on the raised parts of the cog. This way is a little bit less messy, really fast and you can use the cogs right away.
Usually when drybrushing you want to put on a lighter paint on a darker area, but in my opinion it works the other way around as well. I would go for a dark brown paint, or maybe a dark grey. Of course you could instead spray-paint the cogs black and then drybrush them with a light grey or brown colour.