Dedicated to Airbrush 4: Space Marines

Space marine vehicles benefit from the same easy fades as the Eldar ones mentioned below, but the simple shapes of their infantry models makes zenithal highlighting almost automatic.  This means that you can created well shaded/highlighted Space Marines in very little time.  There are a plethora of articles out there on zenithal highlighting, so I won't go into details.  In essence, you spray lighter shades of the base color onto the model from increasingly overhead angles to simulate the glare from an overhead light sources.  After that you paint the details (like guns, etc) you apply the decals and you're done.  I still like to outline the details with black hardlines as well as hit the edges with bright hardlines.  The below picture shows a tactical squad and to the right, an honor guard squad.  The honor guard squad was painted in parts so I could separate the robe portions that needed to be painted tan from the arms and backpacks that would be green.  Additional shade and highlights were added with a brush.