Palm tree clean-up

Hi, need some help regarding the “clean-up” of a palm tree ( washingtonia according to ChatGPT) .
I’m an amateur regarding this kind of clean-up… only thing I usuallys do is to cut the brown leaves.
The owner of the house asked me if I could clean the trunk…
Any tips on how to ? Or is this “not ready” yet?
I did a little bit on the bottom but there are too many loose fiber… I dont know if I’m doing it right.
Thank you for any help 🙂