The project file for this tutorial can be downloaded here.
Step 1: From 'Plugins' tab of the 'Workspace Inspector' create a 'Two Channel Mixer' plugin.
Step 2: Use the pop-up menus in the 'Two Channel Mixer' window to select the layers to fade between.
Step 3: Click and drag the crossfader slider to mix between the layers.
Tip: The fade / auto-fade time can be set in the inspector for the Two Channel Mixer.