I present a slightly old (but still relevant) article on Apple Motion. Here are Ten things you should know about Apple Motion (thanks to DV.com).
Not happy with the alpha channel you get when you cut a Motion project into a Final Cut Pro timeline? Well, your alpha may be off. Final Cut Pro sometimes misinterprets the alpha channel data, expecting you to have a straight alpha channel, when in fact you may have a premultiplied alpha.
1. Select the Imported Motion project file in your Browser.
2. Choose Modify > Alpha Type Black.