In this video the folks over at Allegorithmic walks us through the new Layer Instancing feature within Substance Painter 2017.

The new Layer Instances feature lets you share the content of one or several layers across multiple texture sets. This means that different texture sets can now share a single unified layer stack, reducing dramatically the time spent on the look development phase when working on complex assets. The feature is flexible enough so that you can share the full layer stack or only specific layers and folders, giving you the ability to increase productivity while still maintaining good performance on large projects.