Could I make a decent sour with Trappist Blend (3789) and dregs?

I got a pack of Wyeast 3789 Trappist Blend at my LHBS and I'm trying to figure out what to do with it besides make an Orval clone and I'm leaning towards sours these days. I know it has Sacc. and Brett in it, but no souring bacteria. So...would adding the dregs from a bottle or two of unpasteurized sour beers work to make something like a Petrus Sour Pale Ale? Or should I go ahead and add pure bacterial cultures? Thanks in advance for your advice!

Yes it will work but if I had to guess I would say it's not going to be like Petrus aged pale ale. Petrus doesn't have a strong brett funk to me, it's more of a clean sour in a flanders red/oud bruin way. Pitching that blend with dregs will give you a larger brett colony than you'll have in the souring bacteria from the dregs so there's a good chance the brett will have an opportunity to produce a lot of funk before the dregs can produce a lot of sourness. So you'll likely end up with a more funky sour. That's not necessarily a bad thing.

thanks! i hadn't thought of that.

ended up using it to make this: https://www.homebrewtalk.com/f127/funky-brown-graff-all-grain-biab-366508/