FilmGard is a product that fills film scratches and softens them.
It is a wonderful product for making WetGate. But you have to use a few drops on a cloth and no more.
It retains dust well and I’ve never had any damage using it on my machines, but I don’t use a PTR.
Otherwise, there is also rectified gasoline (I don’t know the name in English), which removes the small encrusted black spots very well.
But here too be careful, the scotch collages do not survive.
If we have a very dirty film, the ideal for me is a first pass with a microfiber cloth soaked in rectified gasoline and then another pass with isopropyl alcohol just before the capture window.