The tool: “Contrast by Detai Levels” at RT has often given me very good results. Is there an equivalent for ART?
Maybe “Loal Contrast” - I get on well with that. Or is the equivalent: “Texture Boost/Sharpening”? I don’t have any experience with this yet.
edit:
I think that with “Texture Boost/Sharpening” I achieve exactly what I did before in RT with Contrast by Detail Levels.
So problem solved ! 
Yes, I think my problem is more than solved. This “Texture Boost/Sharpening” is great for portraits. The skin is not disfigured too much, only a very fine grain is conjured up, which gives the eye support without creating excessive skin blemishes. And the hair, especially beard hair, is rendered very vividly, three-dimensionally.
I am totally thrilled. A first-class tool that I will be using a lot. I’m really looking forward to it.