Painting with the Right and Left mouse button lets you work with two different colors at the same time. The left mouse button uses the primary color, and the right mouse button uses the secondary color.

Since the secondary color is generally used for clearing operations, using it with the right mouse button can be considered erasing. Almost all tools in PD obey this convention. For example, you can use it with the painting tools, the filled and unfilled rectangle, ellipse, line and arch tools, and even the bristle brush simulation. Even picking up a custom brush with the right mouse button erases what was underneath.

Depending on what drawing mode you are using, you may not get the exact results you want with erasing. In pattern mode for example, you will still get a pattern, instead of your secondary color. If you need to, you can switch modes quickly with the keyboard shortcuts.

Picking up a custom brush with the right mouse button erases the original area.

You can also use your brush as an erasing tool by painting with the secondary color.

If you have a tablet attached to your computer and want to take advantage of its features, you can toggle several options on the brush settings panel.

Pressure size lets you alter the size of your brush based on the pressure of your stylus. This option is not on by default, and in some cases and with some tools, you may not want it on. It is a global setting. It is not saved with or altered by any tool.

Pressure opacity lets you alter the opacity of your brush based on pressure. The brush will become more opaque the harder you press.

The tablets eraser is also supported. It will act exactly like painting with the right mouse button, effectively as an eraser.

Pressure size and opacity are also found on the context strip for the drawing tool for easier access.

When you clear an image, you set its color to the secondary color. You can select 'Clear' from the image menu to do so.

However, there are several more options available under the clear button on the tool panel.

You can clear the whole image, or you can clear a 'selection' made with the alpha channel tools, and you can clear to the primary color, secondary color, white, or black.

Example of clearing part of this image selected with the magic wand tool.

There is also the option to clear all the frames of an animation. They will be cleared to the secondary color.