Pulling while repositioning

So I started doing Garuda extreme with my FC group and i landed in the Off tank role and it was there i discovered that I am really horrible at keeping aggro while trying to reposition Suprana and the Spiny Plume.
So i am wondering how the tanks who cleared it manage this. We however managed to clear Garuda Ex thanks for 3 or 4 stacks of echo, and we just dps down sisters who were near the dps because the aggro kept going back and forth between me and the healers while i am trying to reposition the sisters.

Pre-charge enmity combo on Garuda, whack it on Suparna, run to position while Shield Lobbing. Ignore Spiny until someone has 2 stacks and voke it off.

There's another thread in the tank forums regarding this. Several in fact!

What I do as PLD off-tank. Fight or Flight -> Fast Blade Garuda when she lands after feather -> Savage Blade Chirada -> Rage of Halone Chirada -> Provoke Spiny -> Shield lob Spiny -> Circle of Scorn -> Flash -> move to opposite side of main tank.