To make a surface (such as metal) smooth by rubbing it so that it shines. A noun or pronoun can be used between "buff" and "up." I buffed up my car so that it would look nice at the wedding.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
buff something up
to polish something to a shine. He buffed his shoes up and went out for the evening. He buffed up the antique silver platter.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.