-ex on wakeup in certain situations (for example, when reptile throws out a forceball after knocking you down) because it has extended invincibility and further reach
-regular on wakeup to escape the corner
-ex can be used as kinda an occasional gimmick on wakeup with people who duck, because the last two hits connect crouching against high-hitbox characters
-if you catch your opponent at certain heights with regular or ex you can dash up d1~cutter/ex fan/ex lift
-regular can be used as a gimmick in itself as well, as it's +8 on hit, setting you up for things like 33 or a throw. a lot of people don't know anything about its properties so that can catch them off guard
but outside of wakeup? i can't give too much advice for it.