Now I started using progressively smaller brushes, also Smudge and Blur and Airbrush. Smudging the sharp edges left from the hard-edged brush is my most common and favorite way to work. Blur is a bit all over the place, and uncontrollable, while Smudge can act more like Motion Blur if you're careful, and if you use a spotty brush it can look a bit streaky like oil color.
To start adding color, make a new layer, mode: Color. Fill in local color on that layer, in big chunks like this. Fleshtone = 1 chunk, red hair = another, etc. You can also Select a whole area and use Image>Adjust>Hue/Saturation>Colorize on it.
You can also use brushes set to Color or Hue.
Colorized grayscale images tend to look metallic, because on metals the highlight is more saturated and the darker parts are less so (look at copper and gold). This is exactly what you get when you colorize - most noticeable when you apply a flat color on top using 'Color' or 'Hue' mode, but also with 'Multiply' and 'Normal' with transparency.
On most other matter though (especially on semi-translucent materials like skin, hair and bedsheets) the relationship is reversed - shadows more saturated, highlights less. So we can't just apply the single color indiscriminately the same over both shadow and highlight, we need to vary it.
Here I'm refining the colorization further - note the different hues on the sheet and skin, the blue shadows, the reddish shadow-edges etc... it's exaggerated at this stage so that (hopefully) some of it will survive into the final image.
When you've taken this as far as it can go, start using brushes in 'Normal' mode. (Again I use round hard edged brushes, with pressure sensitive opacity mostly, occasionally Airbrush or texture brushes.) You'll know when it's reached that stage, you can feel it - the point of sharply diminishing return. It gets harder and harder to see what you're doing with these modes, since they're very transparent and subtle.
For the next level of subtlety it's best to use straight Normal mode. But if the preceding stage of colorization has gotten you close enough, you won't need to cover all of the image with 100% opacity, you can focus on some areas, which makes it easier.
Now is also the time when I enlarge the image to it's final resolution, to get all the detailing done with the opaque paint.
At this stage I reconsidered, and belatedly went for reference. Since it was hard to find anything fitting, I shot my own. Note: Never copy 1 single reference to closely, if it isn't your own; it's surprising how many beginners don't realise it's against the law to make an image that looks too much like someone else's.
Copyright 2004 Steven Stahlberg.