To refresh one's memory.
重温，再练
To renew a skill.
更新技术，改善
(Baseball, informal)(of a pitcher) force a batter to step back to avoid being hit by a ball pitched close to the body
(棒球 非正式)（投球手）迫使击球手后退以免被投出的近身球击中
improve one's previously good knowledge of or skill at a particular thing
温习，复习
brush up on your telephone skills.
温习一下你给人打电话的技巧。