Dk pvp

Hey guys i have question to Dk players.
Last time i roll on Dk from ninja and now trying some pvp. Im not sure how i should catch someone to start combo. I was trying with; Shadow bullet, Seed of Catastrophe same with air strike and Spirit hunt, but in most cases it doesent work and enemy didint getting stiffness.
How do u starting ur combo?

 

I believe you can find a myriad amount of videos on youtube about PvPing, it is not something that can be explained on a forum page I think.
As for why the "CC's" aren't working as intended (I am not entirely sure but) it may be the same problems remain with the combat mechanics, some do not work and some work too well, BUT it might be something as stupid as the RNG interferring as well as high "CC" resistances.