Sketch using predictive strokes

Sketching > How do I? > Apply and remove paint using brushes >

When sketching, the predictive strokes feature perceives what you’re trying to draw, and redraws it with more precision. You can use predictive strokes to create straight lines, curves, and ellipses.

To use predictive strokes

Choose Preferences > Interface > Hotkeys/Menu Editor , and open the Special > Paint section.
Assign a hotkey to Toggle predictive stroke (curvature) to draw curves, circles, or ellipses, or to Toggle predictive stroke (line) to draw straight lines.
Click Apply.
Choose a brush, then press the hotkey.
The cursor changes shape to indicate the predictive stroke mode you’re in.

Your paint stroke is redrawn when the stylus is lifted from the tablet, or the mouse button is released. The stroke will either be a circle, ellipse, or arc if Toggle predictive stroke (curvature) is on, or a line if Toggle predictive stroke (line) is on.
To turn off predictive stroke mode, press the hotkey again.