Painting With the History Brush
Photoshop CS6 Tutorial
How to Paint with the History Brush in Photoshop
Unless you make a selection in advance, filters affect the entire image. This technique is pretty cool if you want to paint a filter effect in selective areas.
Open an image in Photoshop (File > Open).
Duplicate the background layer by dragging the background layer to the Create New Layer icon (Cmd/j (PC-Ctrl/ j). Name the new layer Source.
With the Source layer selected, Choose an Artistic filter from the Filter menu by opening the Filter Gallery.
Open the History palette and from the pull-down menu, choose New Snapshot. Name it Filter One.
Scroll down the History palette and select the step just before the one where you added the filter.
Click the History Brush and click the box in the History palette next to the Filter One name.
Selectively paint the Source layer with the History Brush.