Instructions : 

Unity
Create a new unity project
Import the latest SDK 3 in your project
Import the Besuru 1.3 UnityPackage

Substance Painter
Import the "Custom_Unity_Exporter.spexp" in ...\Documents\Allegorithmic\Substance Painter\shelf\export-presets
Open the spp file and select the exporter in the Output Templates window when you export your textures
Put the Paddind on "Dilation + transparent" in the export settings

If you don't have Substance Painter you can still use the UV guide in a 2D software