I'm guessing handpainting features isn't at the top of Adobe's priorities for 3d Painter, but having an unlit shader w/ alpha-test and tranparency would be a simple but tremendously helpful option for handpainters. Currently, we have to use "Base Color" in viewport which means we can't see the opacity map which is very limiting.
-- or if anyone out there can share a custom shader for unlit+alphatest or unlit+tranparency, would be appreciated!