Is there a way to vertex paint occluded vertices? Is there a way to vertex-paint-brush vertices that are behind the faces? Kind of like x-ray select, but x-ray paint? There is an option "Front Faces Only", but even if it's off, it doesn't seem to do this (actually I can still paint on backfaces even if this option is on, but not on vertices that are behind faces). Also, enabling x-ray view-through (or wireframe) doesn't seem to do anything to the brush tool.

I would really like this option because I use vertex color in my game as a sort of a "weight" for a shader, so being able to paint a smooth brush over some layered pieces is a must

(working in 2.8)
You need to have 2D Falloff option checked in Brush options and Show X ray view set(not necessary, just to see the occluded vertex) (both highlighted in the image below) It works the same for Weight painting. In all new 2.8 tutorials everybody seams to totally forgot about using this feature and I was so frustrated, when one by one everybody was just painting around objects. Finally found the answer and am happy again :)