Painting an image in Photoshop involves selecting a brush and applying an effect to an image. This task outlines the basic procedure for working with any of Photoshop's painting tools, regardless of the effect you are applying or the kind of file to which you're applying it. Photoshop makes available the Airbrush, Paintbrush, Rubber Stamp, History/Art History Brush, Eraser, Pencil/Line, and Sharpen/Blur painting tools and the Dodge/Burn/Sponge tools.
Select the Brush Tool
Open an image file. Click the Paintbrush tool in the Photoshop toolbox.
Choose a Blending Mode
With the Paintbrush tool selected, choose Normal from the Mode menu in the Options bar.
Set the Opacity
The Opacity slider controls the density of the brushstrokes applied by the tool. Click and drag the slider to a lower setting for more transparent effects; leave it at 100% to paint with a completely opaque stroke. The Flow slider controls the feather of the brush. Combine Flow and Opacity to create the proper balance of transparency and soft brush strokes.
Choose a Brush
Click the small arrow next to the Brush icon in the Options bar to open the brush palette. Move the Master Diameter slider to set the brush size, or select a preset from the list. To avoid painting the image when you click, try clicking in an empty space in the Options bar.
Paint the Image
To apply the paint effect, move the cursor into the image window and click and drag.
Grouping Similar Palettes Together
You can group similar palettes together by clicking and dragging the palette tab and moving one palette onto another. You can also drag palettes to the palette well on the right side of the Options bar.
Tapping in Big Brushes
To modify a large area without leaving telltale brushstrokes, use a large brush with a light Opacity setting. Instead of dragging, position the brush over the area and lightly click the mouse. Click repeatedly while moving the mouse slightly to build up a gradual effect.
Setting Brush Size Preferences
You can set the Paintbrush cursor so that it appears as the currently selected brush size rather than as a tool icon or a set of crosshairs. This way, you know exactly how large the brush is (its circle icon shows you) in relation to the resolution of the image; you have a better sense of where you will paint the effect. Choose Edit, Preferences, Displays & Cursors and click the Brush Size button in the Painting Cursors section of the dialog box.