whoa, pretty broad question there.
before I begin, I need to state that
I use a WACOM graphire3 tablet for all digital work; none of it is done with a mouse.awright, then. For
digital coloring:Photoshop:
If I am using a pre-drawn lineart, I first clean it up [if necessary], then set the lineart layer to "multiply", and add new clear layers
beneath it to color.
There's 2 things that need to be stated here, because of what I'm aiming for in the picture - realistic or more cartoonish.
when I want to shade more realisticly or smoothly, I do
not ever use dodge or burn, and if I actually do, it's
very rarely. I much prefer picking out colors seperately on the palette and testing them if they make good shadows/highlights [choose a color close to the base one]. Dodge/burn is much more limiting and you have to be a lot more careful with it. But that's more general. Anyway.
After I lay the flats down, I proceed to pick out a new color, then lower the brush opacity to somewhere around 10% [changing it and the brush size now and then depending on what I want to do], then proceed to color. Opacity is a very nifty feature, since you can color very lightly then more dark as you add more strokes

I can't really describe how I work from here on out, except I keep layering it as it gets darker/lighter until I reach something I'm satisfied with.
When I want to shade more cartoonish [cel-shading], I just lay down the flats, then on a layer
directly beneath the lineart but
above any color layers, I set the new layer to "multiply", pick a shade of grey, and color over the parts that I want shaded. Very easy, doesn't take nearly as long as the first.
OpenCanvas:
Mostly leaning to the 'realistic' stuff, but can also be used for cel-shading [but cel-shading is easier for me to do in Photoshop]; blending is very easy here so long as I don't press hard with the pen [don't know about mouse use]. Since I use a very simple version of the program, very very little can be done with layers and filters, so it's always done entirely by hand.
for
traditional coloring:
'traditional art' is art made with the use of markers, colored pencils, regular pencils, ink, charcoal, etc. for those not familiar with the termMarkers: I use Prismacolor markers. Good markers, buy them if you have talent and can afford them.
Since you have to work quickly with Prismas [it needs to be still fairly 'fresh' to blend well], I don't do realistic shading with them. I lay down the flat colors as fast as possible [so there aren't any streaks], give it a minute to dry, then using the same marker color where I want shading [unless I already used a grey marker before putting the actual colors down].
Same with when I want patterns on clothes, I usually keep the cloth and pattern the same color so when the base dries, I can add the pattern.
Lighter parts are either done with this Sakura opaque white ink pen, or with a white prismacolor colored pencil.
Or I just avoid coloring in the parts that I want to look light and use a lighter but similar color, or none at all. :p
Colored Pencil:
I prefer using more realistic shading for this. Just pick out a color, and press lighter where you want it lighter. There's a much more time-consuming but better-looking-result way where you take one color and, without changing the pressure of the pencil on the paper, keep coloring over specific areas until it looks the way you want it to.
I have no idea how to describe how I mix my colored pencils and markers together, so I'll end it here.