Hello my second Threat and i have got a Question again

Yesterday, I tanked Sophia and after every Tankbuster me and my OT had to swap
but it was a bit hard to get the enmity from a WAR the problem is that I dont know what better is

First Provoke then Grit and enmity combo - With this way i had some problems because Grit is a GCD and until I can make a enmity skill he took another AA and died sometimes

First Provoke and enmity combo without Grit and turn it later on?

Do I have to know the Tankbuster so I'm prepared to turn my Grit on?

So I am just asking if there is a easy way to Tank swap as a DRK

Greeting Kenny