Has anyone got any tips for cleaning before varnishing internal doors?

I keep reading differing opinions on Google & now I don't know what to do for the best as I will post a direct link in post 1 to the new doors I've had fitted and the Joiner has left a lot of dirty fingerprints on them and I don't know what to clean them with before varnishing.

Some say to use White Spirit then others say not to as it leaves a residue ,some say use a Tack cloth and others say not to etc etc

So now I'm back to square one not knowing what to use as just a wet cloth won't remove them I've tried.

Has anyone had any personal experience with this please?