Ah I see. Well again it depends on the fight. Take a8s for example, after the full-metal Faust phase I use pain flare and bane to burn down the adds, fester on the alarum, then enter DWT when it's safe to burst on the boss.

On the standard dungeon bosses personally I try to space out my Aethertrail stacks. If you blow your load and enter trance as soon as its up, you'll have about 30 seconds of spamming ruin until aetherflow is up again. I use the standard 2f1p opener, then use 3festers while maintaining dots until I can trance again.