The smart brush tool is similar in use to the Pull tool, but is better at fine detail work. You pull from an existing selection into another area to extend it. You can lock selections in exactly the same way as you would with the Pull tool.
There are 3 different modes for the Smart Brush. Use the drop down menu next to “Find” to switch between them.
Solid, Opaque Areas detects larger, hard edged areas, like branches or girders.
Feathered, Translucent Areas detects edges that are not well defined, or objects that are either partially or wholly translucent. Use on grass, and finer edges to trees or plants in the distance.
Everything inside brush stops the brush being ‘smart’ and looking for edges. It will now act like a normal solid brush.
Tips: When the Smart Brush is selected, you can switch between the modes by pressing S, F or V on your keyboard.