lubing the sunroof rails

[RKreutzer]

Hi everybody,
my sunroof is still working, but it hesitates at one spot on the way to close. I did buy the MB lube, but I am not quite sure what all to lube. There are some scuff marks on the inner rail facing up and it did not have any grease on them. But I think the main lubing should be inside the U-channel, right? Any good tool to do it or do I need to bend some wire from a coat hanger and wrap some rag around, dipped in lube?

Also, what do you lube in the back? (see 2.nd picture)

Thanks for your help.
Reinhard Kreutzer