Imagine a judo practice.The martial art guide tells one of his (help me to find a word) that he has to improve his upper cut.Is there an alternative for 'improve'? Like 'give emphasis on your upper cut? Doesit sound natural and correct?
Just in case Dr. Nick's humor wasn't clear to you, student is probably the best choice.
(Improve is also a good choice. Give emphasis to does not sound natural.)