Using masterslides: layers?

From what I can tell, a layer added to the Master Slide doesn't automatically transfer to the Master Layouts. So you'd have to manually add the layer to each Layout. 

Rather than use a layer, you could just give the icon a hover state that includes what you want on the layer. If that icon-with-hover-state is on the Master Slide, it'll appear on all Layouts. 

You can an icon on your slide master that triggers a layer that appear on all of your slides. I'm attaching a couple of screen shots that might help - I had three icons on my master slide and two layers.

You would just need to add your icon to your slide master. Create the layer on the slide master with the information you want to appear. Then create the trigger on the master for the icon to show the layer.

You won't see these layers being copied when you create new layouts. However, they are always there in the background since it is on the master. Anything on the master applies to every slide. 

Ah, I see now that the layer is not visible, but it is there in all the layouts. Thanks!