In Sketchbook Pro 5.x you could easily see your custom brushes in the Brush Palette after you created it. That behavior has changed for the worse in Sketchbook Pro 6, making the process of selecting your custom brush a two-click affair.
Now the newly created brush appears within the Brush Library, a pull out menu that displays when you click on the icon that resembles three stacked rectangles on the upper right hand corner of the Brush Palette.
It can be incredibly tedious to have to constantly click the Brush Library to access your favorite custom brush. Thankfully you can easily drag your custom brush from the Brush Library onto the Brush Palette (see image above).
The only downside is that your custom brush setting will replace the existing default brush in the Brush Palette. But, given how I never use the default settings anyway, it’s not a big deal. You can always reset your Brush Palette back to its default settings by way of the Sketchbook Pro 6 Preferences menu.