The Stroke Animator option
This option is accessible in the Edit > Preferences panel directly under the General tab. Like it was said in Lesson 1, this option allow you to draw over several frames. With the [Ctrl] key pressed during the drawing, the current frame will change automatically.
Here is an example, choose the Free Hand Dot option with the Pen Brush tool. Create a layer which has around 30 frames and place the current frame to the first one.
Now, press the [Ctrl] key and start to draw. The current frame changes during the drawing. And when the last frame becomes the current one, the drawing starts again on the first frame. And when you stop drawing, you will see one (or more if the animation has looped during the drawing) dot on each frame.
This feature is really useful to animate decorative elements, fireflies flying in the night, annoying insects, water jet...