Once you've washed and drybrushed, outlining is an easy way of establishing the darkest shadows on a figure, as well as making a strong division between two bordering areas (i.e. between an arm and a torso, or between armor and flesh). Mix up a darker shade of the basecoat, even darker than your wash color was, and thin it down almost as much as the wash. You can use a little black paint to darken the outline color, but avoid using straight black to outline, as the look is very harsh and artificial. Take a 10/0 brush with the paint and run it along the seam between the two areas. While still wet, blend the paint a little into both areas.
This will make a nice, deep shadow effect. You can also use the outlining color to darken areas of the base color that would normally be in shadow on the miniature (underarms, under crotch area, etc.)
Inks can also be highly effective in outlining also. Use them straight from the bottle for the best look.
This is the Rolls-Royce of miniature painting. A well-blended figure can look very striking on the gaming table or in your collection. Blending is not for everyone, however, as it takes patience, a steady hand, and lots of practice!! (Here's where your visor comes in real handy, too). This technique replaces the wash/drybrush method for painting most areas of a miniature.
If you plan to try your hand at blending, start with a miniature that has vast, unadorned surfaces, such as a wizard with a large cloak, to help you learn the technique. Larger-scale 28mm miniatures, such as those made by Games Workshop or Heartbreaker, are also easier to practice on.
I mix up all the tones I'm going to blend with on my palette; I generally use 5 shades of paint for a good blending range: highlight, light, basecoat, dark, and shadow colors. The basecoat color will be your 'midtone' color on which all of your blending shades will be based. You'll create light and dark shades from it, as you would with the drybrush/wash method, but making two tonal steps in each direction from the basecoat: two progressively-lighter and two darker colors. The highlight shade should be very light (think of the reflection on a surface) and the shadow shade very dark (as an outline shade would be).
A word of caution here, though: be careful about using too dark a basecoat when blending light colors (yellow, red, flesh, etc.), because if the basecoat is too dark, blending a lighter shade on top of it makes the lighter paint look chalky, or like it's floating on top of the darker layer underneath! For these colors, I recommend starting out with a very light basecoat, and using the dark and shadow tones sparingly.
Do a quick wash and drybrush of the basecoat to begin with; it doesn't have to be perfect, as this step is merely to establish the locations of any shadows and highlights you'll want to blend later. Now thin your paints down to blending viscosity: you want them to flow well enough to enable you to blend the colors on the figure readily, but not be so thin that the pigments become too diffuse to cover up the basecoat. The consistency should be between that of a basecoat and a wash; you'll have to experiment a little to find what consistency works best for you. A touch of acrylic blending medium (available from an art supply store) can increase the paints' drying time to facilitate blending.
I blend the paints 'wet on wet' directly on the miniature, meaning I intermix one tone of color into the previous one using the same brush. An alternate blending method is to paint the two tones of color right next to each other, and use a separate, slightly damp, brush to mix them together. The key with either method is to mix only the boundary area where two colors meet, which causes a natural-looking transition of tones. For this reason, I recommend using a fine paint brush (10/0 or so) to facilitate blending these tricky transitions on such small spaces.
Start blending by painting a layer of the thinned basecoat on the section you're blending (say a fold of cloth). While its still wet, lay down some of the light tone, about mid-way up toward the highlight, and blend it into the midtone. Then blend immediately into the light tone with the highlight tone, again about halfway toward the final highlight. As you work, the paint should be blended gradually 'upwards' from the midpoint of the basecoat color towards the highlights, until the highest point of the area has the lightest paint.
Now follow the same procedure for the shadows, blending toward the shadows (rather than the highlights), from basecoat to dark to shadow tones. I usually try to reserve the shadow tone for only the deepest shadows; it serves much the same purpose as outlining does.
If done right, the transition of colors should be seamless. Don't be afraid to put down more basecoat paint and reblend an area if it doesn't look right. You can do this a few times before the paint begins to get too thick to work with. Or, if you find the paints are too watery and simply aren't blending together, but instead swirl around on top of the basecoat (sometimes leaving a 'hole' through to darker colors beneath), you should wait until the paints have dried out a bit to lose the excess water.
Since the blending process can take some time, your paints are libel to start drying out on you; just add a drop of water or blending medium when you feel they are getting too thick. Finally, if nature calls, or you need to take a break or go blind, wrap your palette with some plastic wrap to keep the paints from drying out; if you let them dry out, it can be pretty hard to mix up new shades of paint that exactly match the old ones.
Armor and other metallic surfaces are easy to achieve. Buy the best metallic paints you can find: I use Polly-S metallics, which are now available under the Polly-Scale line at modeling hobby stores. These paints coat very evenly and dry very smooth, making them ideal for washing over with inks and as undercoats for other metallic colors. I do use other brands of metallic paints, but most are too thin to be used as a basecoat: Citadel metallics and some craft paints fall into this category. A word of caution about craft paint metallics also: open up the bottle before you buy it and check the fineness of the metal flakes in the paint. The finer the flakes, the better, as thick flakes make the metal look grainy when it dries, rather than smooth.
There are two main schools of thought about doing metallic armor: the quick and dirty method is to paint the armor black, then drybrush with your metallic color of choice. This is easy to do and can yield good results, but the armor will never look like shiny, dress plate mail... But if you want the battle-worn look, this is the way to go.
The other method is to paint the metal color first, then wash it with an appropriate ink color, and either drybrush or blend metal paint on the highlights. This is better for the dress armor look some miniatures need, such as your paladin figures. I use this method for painting any jewelry, bracelets, etc. a miniature might have, as its better suited for representing precious metals.
Besides the usual gold, silver, and brass paints that are available, there are colored metallics, such as red, blue, purple, etc. available from Citadel, Ral Partha, and craft paint companies. To use these, I either drybrush them over black, or, for the 'bright metal' look, I undercoat them first with an appropriate Polly-S color (silver for blue or purple, gold for red, etc.) and paint on a layer of the colored metal paint over the Polly-S. Then I finish them as above.