Chris has just posted the video, audio and slides from my Xaminar on Thursday, on how to style your iOS apps using UIAppearance. Obviously, the samples and code are in MonoTouch, but any Objective-C developer with half a brain should be able to do the mental translations.
I've put the sample project (and slides in PDF form) on GitHub, and Chris has also put it into the official Xamarin repo.
Styling your iOS apps with Nic Wise
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