Is there a way to force photo to look and name faces/people?

No, we just have to let it get on with it at it's own (glacial) pace. I swear to god, I'm sure a snail could crawl to the moon faster.

Just make sure you have manually named enough faces of a person for Photos to recognise a similarity. Not just one or two.

And Photos is only using automatically found faces circles to learn what a person looks like, not the circles we add to a photo. we have to find the photos with empty names below the faces circles.

Photos may have already detected most faces you are looking for, but split across several different people albums, because it has not been able to confirm that they are the same person. If the many split albums are small, they will not appear in in the people album. To be able to join the fragments, you have to name at least one photo in each of them.

I am using a smart album with the rule "Person is " (leaving the name empty) to find quickly faces Circes with an empty name below them.