I am bad at this game so I'm a bad person to ask for advice
but since you asked
standing fierce and fireball a lot. that's pretty much it. if you think they won't anti air you you can jump in with fierce x2. if it hits then you can immediately combo into launcher combo. if it doesn't, you can mix up with either standing jabs or throw. or just fierce more.
I know it sounds basic and pretty braindead, and it is! I wouldn't call my Chun play high level.
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http://www.youtube.com/watch?v=npHDxSvwCE0