"用手梳头发"的英文表达方法有很多种，其中一种常见的表达方式是 "brush one's hair with one's hand"，这个短语的意思是用手梳头发。下面是一些英文例句及其中文翻译：
She brushed her hair with her hand to get the tangles out.
她用手梳头发把打结的头发梳开。
He brushed his hair back with his hand and smiled at her.
他用手把头发梳回来，对她微笑。
She brushed her hair with her hand as she looked in the mirror.
她在镜子前用手梳头发。
这个短语的来源可能源于日常生活中人们经常使用手来梳头发的情况。在英语中，"brush" 是梳子的意思，而 "hand" 则指手。因此，"brush one's hair with one's hand" 就是用手梳头发的意思。