With App Press you can quickly build your app for one device and then copy the content to another device type. For example if you have an iPhone 6s, build the app for that layout so you can actively preview the changes that you make to the app using App Press Now.
After you have completed the app and are satisfied with the way it looks and functions, you can copy and paste the assets over to the iPhone 4, Android Portrait, and Android Widescreen layouts. In next to no time you can build out your app for app supported devices with simple copy, paste commands.