Decanting a commercial yeast harvest

I'm trying to create a starter of harvested yeast from 6 bottles of Bell's Oberon Dregs. My only remaining question is really just how do you decant? So far, I've made the initial starter of DME, water, and dregs. Let it sit for a few days, cold crashed for 24 hours. There is a cake at the bottom (hard to differentiate the trub from the yeast cake.

Do I pour off the wort, leaving the trub/yeast a the bottom to use for my step up? Or am I supposed to pour off only the yeast?

Generally, you'll pour off the old wort. Then you can either pour in a little pre-boiled, chilled water and re-suspend the yeast, to pitch into your step-up, or pour a new, slightly-higher OG wort on top of the cake, and let it go to town.

refer to this thread, which is, ironically, a few threads away from yours on the same page:
https://www.homebrewtalk.com/f163/pacman-progress-my-first-bottle-harvest-325680/