Mypaint is a digital paint programme that concentrates on providing a clean and efficient workspace for life-like material emulation.
There are advanced features in Mypaint, but the basics are sublimely simple. Mypaint puts a heavy emphasis on a clean and minimal workspace, giving you a screenfull of blank canvas to fill up.
Mypaint is so good at what it does that it can usually make even the most rudimentary illustrators look good. (This is taken from personal experience.)
Mypaint is a fairly minimal application, both in design and configuration options. If you draw all day long, you might prefer to use an environment that allows you to customise it.
Install Mypaint from http://slackbuilds.org.
The most commonly used palettes in Mypaint are minimised in the upper right corner of the MyPaint window; there's an icon for the colour picker, the brush presets, layers, a scratchpad for testing out brushes and colour mixing, and full-screen mode.
Along the top toolbar on the left are the less-frequent, but no less important, controls. Particularly important is the drop-down contol panel for a brush's size, opacity, and precision. The Slow Position Tracking setting is MyPaint's term for precision, and it can be extremely useful if you find that the computer is translating every little movement that you make with your tablet or mouse, but you would rather it pick up on only the broad, important strokes, then increase the Slow Position Tracking value. This means that MyPaint will intentionally delay its detection of brush movement. This means that you can make rather clumsy movements across your desk or tablet and still end up with smooth and flowing brush strokes on the screen.