Here's an example, I highlighted the reused UVs in red, and the UV seams are pink. The reused UVs are offset in UV space 1 whole unit, which is purely optional. This way they reused bits are easier to see in a UV editor, but because the texture is tiled, they end up getting the same texture anyway!…
I don't have Substance installed right now and don't remember, but can you turn off texture filtering in the viewport? SeanWink: In addition to the great info you already got, turning off texture filtering can help you see what you are doing a bit better at lower resolutions and provides a crisper render as well. It's not…
So, did that help at all? Curious if you have any questions. It's a really cool technique, and there are some additional tricks I've seen people use that are really nice, like what I call 3/4 mirroring. Where you mirror the UVs of a face, but not down the midline. This lets you have different eyes or a diagonal scar, but…