brush up vs scrub up

brush up

verb
  • To paint, or make clean or bright with a brush. 

  • To review; to improve an existing but rusty or underdeveloped skill. 

scrub up

verb
  • To clean or wash by scrubbing. 

  • To dress up. 

How often have the words brush up and scrub up occurred in a corpus of books? (source: Google Ngram Viewer )