Ask early, as early as possible. Use standard ATC english as that is all they understand. They also understand the word "Require". We "require" 20 right due to weather.
If that doesn't work, have your FO ask in Chinese.
If that doesn't work, tell them you are doing it, and do it.
Very,very, occasionally it is a little difficult. It is always manageable. Normally it is the same as everywhere else.