Radak: It is normal for people to pull out their hair amidst mourning. The beard is the glory of the face. At a time of mourning, one shaves it to remove the beauty of his face. And so it says "Megulchei Zakan u'Keru'ei Vegadim" (41:5). Also Yonason translates like this. It says "Geru'ah" in place of Megulachas, for detriment.

Radak: The skin is scratched and wounded; this is like "Lo Sisgodedu" (Devarim 14:1). Gedudah has the same grammatical form as Meluchah and Chalushah.