He spent three years combing through Qing dynasty archives.
Tips
memory
Literally 'crawl' (爬) and 'comb' (梳) - picture combing through tangled hair strand by strand. The image carries over to working through messy historical records or data.
register
Bookish - common in academic writing, journalism, and editorials, rare in casual speech. Use 整理 (zhěnglǐ) instead in everyday contexts.