The Paint Brush and the Airbrush work in similar ways. Both create strokes of color in a selection or an image and have a variety of options for changing the brush stroke.
The Paint Brush tool creates strokes of color that simulates an artist’s paint brush. Brush strokes can have hard or soft edges. The Airbrush simulates an airbrush or spray can, and is time-dependent, meaning, the longer you hold the brush over an area, the more the brush produces the effect.
To use the Paint Brush or Air Brush:
On the Tool palette, choose
the tool: Paint Brush 
or
Airbrush 
. (These tools are
grouped together.)
Choose the foreground and background colors and materials. See Basics of Using the Materials palette.
On the Tool Options palette,
choose a shape: round 
, or square 
. For
information on creating your own brush tips, see Creating
Brush Tips.
Note: To create rectangular, elliptical, or angled brush tips, start with the round or square shape and modify it using the Thickness and Rotation options.
Specify the brush options such as size, opacity, hardness, thickness, and rotation. See Setting Brush and Paint Options.
Note: See the Adjusting the Brush Size via the Keyboard section below for details on adjusting the brush size without moving the cursor off the canvas.
For the Airbrush, in the Rate edit box select the rate at which the brush applies paint (from 0 to 50). Use a value of 0 if want to apply a consistent amount of paint. Use higher values if you want more paint applied when you drag the mouse slowly or pause the mouse.
Note: To reset brush options to their default values, on the Tool Options palette click the Presets drop-down list and choose Default.
Drag in the image to paint as follows:
For all painting tools, to apply the foreground material, drag with the left mouse button.
For all painting tools, to apply the background material, drag with the right mouse button.
For all painting tools, to paint a straight line, click once at the beginning point, then press Shift and click the end point. To continue the straight line, move to the next point and press Shift and click.
For the Airbrush, to build up color in one area click and hold the mouse at one position.
Undoing paint strokes:
When you are applying paint strokes, the Undo command (or the History
palette) is very useful. To remove the most recent stroke, click the Standard
toolbar's Undo button 
, or press Ctrl + Z, or undo the stroke via the History palette.
To undo multiple brush strokes, press Ctrl + Z multiple times or use the History
palette. If you undo too many strokes, click the Standard toolbar's Redo
button 
, or press Ctrl + Alt + Z, or redo the stroke via the History palette.
With the exception of the Warp brush, you can quickly adjust the size of any raster brush (including the Clone brush and the Background Eraser) as well as the Art Media tools without taking the cursor off the canvas and into the Tool Options palette. To adjust the brush size via the keyboard:
Press Alt + X to decrease the brush size by one pixel.
Press Alt + C to increase the brush size by one pixel.
Hold down Alt and Shift and press X to decrease the brush size by 20 pixels.
Hold down Alt and Shift and press C to increase the brush size by 20 pixels.
Hold down the Alt key and drag the left mouse button up or down to rapidly change the brush size.
Hold down the Alt and Shift keys and drag the left mouse button; the size will be set to its lowest value (3 pixels for the Art Media tools, and 1 pixel for the raster painting tools) and then you can drag to increase it from there.
Setting Brush and Paint Options
Undoing and Redoing History Palette Actions