I always coat the grommet with dielectric grease, I suppose any lite grease would work, before installing. I’ve also made a rounded wooden dowel, so I don’t cut it, to help force it in place.
It sorta the competitor shop owner was complaining about how it was to install fuel lines. Then Had him try in my shop and seen he was pushing instead of pulling the lines. I showed how I did it and he went away a happy camper.