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1. New document Go to File>New. Set Height/Width to 200 pixels, 180 pixels/inch for Resolution, Grayscale for Color Mode, White for Background Contents. Hit OK. Pick a standard hard round tip in the Brush Picker. Hit D to restore default Foreground/Background colors.
2. Paint the footprint Start to paint the footprint of your brush. We’re making a hairy brush, so we’re painting thin horizontal lines close together. Making these ragged will add a natural feel. Use the Rectangular Marquee tool to make a selection around your painted brush tip.
3. Trim and save In Image>Trim, pick Top Left Pixel Color and check all Trim Away boxes. Hit OK. In Edit>Define Brush Preset, enter a name for the brush and hit OK. You can close this file without saving changes. The new brush will appear in the Brush palette thumbnails.

How to Make SWF Background Invisible (Transparent)