Both. Aerate and pitch the US-05 as normal. Pitch the bugs at the same time as the US-05.
Unless you've done a few starter steps, the starter and dregs won't be enough for a healthy, relatively fast-starting primary fermentation.
Also FYI: Petrus Aged Pale does not have viable brett/bacteria, per The Mad Fermentationist (I believe both the Aged Pale and Oud Bruin are pasteurized):http://www.themadfermentationist.com/p/dreg-list.html
You might hedge your bets a bit by either adding the dregs of a few more sours or a commercial blend (Roselare, lambic blend, etc). You'll definitely get bretta from the Oud Kriek, but often the bacteria in dregs can be weak and take a long time to develop acidity. Working the dregs up in an aerobic environment (starter) usually KO's the pedio, and lacto is often fleeting/absent in lambic because of aged hops, low pH, and time.