When using vrayRE_Light_Select, a good practice is to have one vrayRE_Light_Select pass for each light source in your scene. This way the Lighting element can be recreated from them, and adjusted as needed while compositing without re-rendering.
If the vrayRE_Light_Select element Type is set to Direct Illumination, the specular contribution is added to the render element. While this is perfect for simple compositing, a better workflow is for each light to be selected for two Light Select Render Elements, one with its Type set to Direct Diffuse and another with its Type set to Direct Specular. In this way, the specular and diffuse lighting can both be controlled independently at a composite level.
When VRayFastSSS2or or Al Surface MaterialSurface Materialis used, the SSS render elements should be added to the composite with a plus operation to the Light Selects.
In order to use VRayLightMesh properties with LightSelect render element, add the vrayLightMeshProperties_lightlinknode to the LightSelect node.