Use the brush controls
Whenever a photo is selected and displayed in the Viewer or in full-screen view, you can retouch it using a brushed adjustment, which allows you to manually target a specific part of the image using brush controls. Most adjustments can be brushed on images. You choose a brush for an adjustment from the adjustment’s Action pop-up menu.
In addition to brushing standard adjustments, you can also use Quick Brush adjustments that are specifically designed for brushing on images. Quick Brush adjustments are accessible from the Add Adjustment pop-up menu in the Adjustments inspector and the Adjustments pane of the Inspector HUD, as well as from the Quick Brush pop-up menu in the tool strip.
When you choose to brush an adjustment, its Brush HUD appears. You specify settings using the controls in the HUD and then brush the adjustment on the image.
When you choose a Quick Brush adjustment, its adjustment controls appear highlighted in the Adjustments inspector and the Adjustments pane of the Inspector HUD, if both are shown. As with the standard adjustment controls, you use the checkbox for the adjustment to turn Quick Brush adjustments on and off. For more information, see Remove adjustments. Some Quick Brush adjustments also have sliders for changing parameter values after the Quick Brush adjustment has been applied. For more information, see Use sliders.
For more information, see Apply brushed adjustments or the topic for a particular Quick Brush adjustment.