If you don't mind painting the armor first, "dampbrushing" and drybrushing can be your friend. I like my space wolves in a medium to light grey that's fairly tone neutral, but the same technique can be used for other colors. I start by basing in black and then working up; pretty much the opposite of the "wash" process described above.
There are two operative questions when I "drybrush" miniatures: how quickly and how heavily. If you want a rougher, more mottled look, you'll use a lighter bottom layer and let your subsequent layers dry more or less completely before applying the next. The end result will be a little like this:
For a more even look, that appears completely colored to the casual observer you might add layers more quickly, blending them together either on your model or on the palette. This will lead to something that looks more like this:
All manner of variation between these two approximate extremes is possible.
(Note: I use craft acrylics, generally undiluted. Your results will vary somewhat with thinner acrylics or enamels, but the basic techniques still apply. I learned all these tricks with enamels and adapted them to acrylics. In general, you can paint more slowly with anything else and still blend successfully. You will need to wait longer between coats with thinner, slower drying paints if you don't want blending.)
The basic techniques are as follows: to "dampbrush" either load your brush lightly, paint directly onto the center of highlighted areas and pull out, making the paint more thin and uneven at the edges, or load normally and pull your brush once per side lightly across dry part of the palette, and proceed as above. To get a more "rocky" look, wipe the paint off onto the palette several times (until the amount of paint on palette and brush is similar) and proceed as above. You'll still get nearly full coverage on highlighted areas, but shadows and gaps will develop more quickly.
True "drybrushing," where you systematically wipe the overwhelming majority of the paint off your brush onto a dry rag and then perhaps swipe lightly once or twice to lighten the load still further, can be used with a light color to "dirty" things up just a bit, or to give them a textured look. (Depending on color.) I always do this for large areas, more or less without exception.
To blend, you add light paint to the high spots of still damp (not yet tacky) darker paint. This can be done on the model, or on a wet patch on your palette. If what you get is too light, load up from your palette with darker paint from the same family and blend again until what you get is a suitable shade and as even as you wish it. (It will virtually never be truly even. You will almost always get nice shadows this way.
Layering is almost an independent variable and refers to the number of shades. One shade on black will give you an acceptable, but rather flat look. Two shades (a medium and a highlight color) will lool better.) Three shades can give you a quite nuanced look. For large areas I typically use at least three, for small items like belts and small bags I will frequently use two. I'm a little lazy about metals and typically just use one dampish coat of a metalic paint, though you can get quite nice results with a related color and a metalic on top of that. (Say yellow or brown beneath gold and white or grey beneath silver.)
As to paints, I'm a big fan of craft acrylics. They're cheap and work well. I've seen good results with artists acrylics. I gather that they're even cheaper still, but require a little more skill, since they come as a nearly dry paste and you thin them yourself in small temporary pots rather analogous to a palette, but with more water.
Anyway, not sure if this helps much, but it's a good way to achieve a quick, but still relatively characterful paint job. The more "mottled" you go the more dark and dirty your miniatures will look. Smoother and more blended will look more typical Rogue Trader era GW.
