Creating a custom animation with CGLayers?

Question

Basically, I want to animate a shrinking circle. I've already done this by drawing progressively smaller circles onto CGLayer's, and then using

if(index < 30){
[self performSelector:@selector(showNextLayer) withObject:nil afterDelay:(NSTimeInterval)0.02]; index++;
}

in my showNextLayer method. This works for my simple goal, but in general is this a more or less sensible way to draw a custom animation?

Apple has a lot of documentation on animation -enough to confuse me-, but as far as I -finally- understand:

1. The animation services provided by UIView is good for animating some basic view properties, view transitions etc.,
2. those provided by classes that inherit from CAAnimation, are good for animating properties like color change, 3d transformations etc.
3. UIViewImage is good for animating custom bitmap images (and it is not a good idea to create bitmap images when you can just draw circles into a CGLayer instead).

It seems to me that displaying the contents of a sequence of CGLayer 's would also be supported, am I missing something?

Thanks in advance for any clarification..