It sounds easy, doesn’t it? Duplicate one layer’s layer mask on another layer. It is easy but only if you know the technique. A layer mask is a channel that determines the visibility of the content of that particular layer. If multiple layers require the same areas of transparency, you can create a single layer mask and copy it to the other layers. We’ll start with a look at creating layer masks. A layer mask enables you to create areas of transparency on a layer without erasing the layer content. Since the layer’s entire content is still available (although partially hidden), you can later edit the layer mask to change the visibility. NOTE: Keep in mind that a layer named “Background” (in italics) cannot have areas of transparency. Simply double-click the layer name in the Layers palette and rename the layer. That converts the layer to a regular layer, enabling you to show/hide areas selectively with a layer mask.
Creating Layer Masks
A basic layer mask can be created by making a selection of the area of the layer that you want visible and then clicking the Add Layer Mask button at the bottom of the Layers palette. In this example, the Horizontal Type Mask tool was used to create a selection in the “shape” of a zip code.
As I've been learning to create a set of layers. Starting out with a few basics to truly get the hand of duplicating, this tutorial will help you immensely.