I’m a SoCal player but I never use PSN anymore… if you’re ever on PC let me know!
In general though, the Chun matchup is very tough for Gief. But once he gets a single knockdown, it can usually lead to many more and usually shift the match in Gief’s favor.
Ultimately it comes down to footsies, knowing the ranges at which Chun’s far HK and far HP can hit, and the reactions to green hand through a fireball if she is reckless enough to throw one out while you’re walking forward. Jab SPD is hugely effective because of Chun’s large crouching hitbox - it will grab from ranges that seem stupidly far away. After that, it’s really just a mixup of what Chun is going to do on wakeup - usually either backdash, EX SBK or just sit and block. Green hand beats backdash, block beats EX SBK, SPD beats block. Mixing in the short-jump j.LK into Flying Power Bomb works well too.
Time to practice dat Rock Paper Scissors!