Create a custom texture brush by opening a texture photo. Press Cmd/Ctrl+J to duplicate and Cmd/Ctrl+Shift+U to desaturate. Activate the Marquee Selection tool. Shift-click and drag an Elliptical Marquee selection to fit into the middle of the texture. Press Shift+F6 to open the Feather Selection option, setting Amount to 25 pixels. Press Cmd/Ctrl+Shift+I to invert the selection and hit Delete. Create a solid white layer beneath your texture, select your texture and press Opt/Alt+Cmd/Ctrl+Shift+E to merge visible layers into a new layer. Go to the Edit tab and select Define Brush Preset to add a new brush to the Brush palette.