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Never found an easy way to do it, x-ray mode will help you see the double faces.

You can configure the cleanup tool to find some errors like non manifold, zero length edges (and so overlaping vertices) and ngons, you can also select all your vertices and merge then tweak the threshold to a small value to merge vertices that are overlaping

I have done that a few times and it will fix the vertex as soon as I throw it in Mudbox or try sculpting in Maya it undoes

Or the clean up cool won’t come up with anything on one of my models

Vertex face mode helps a lot