Believe that stone uses WLP007, or something similar in a proprietary yeast for their beers. Never done Double Bastard before, but have done it in an AB clone.
As to your question on reuse of the yeast, I'd wash it first and only use the prescribed amount via MrMalty.com. When I read Lemon Grass I don't want anything close to that in my DB...
Kegged: Waldo Lake Amber, Notty as Helles, Vanilla Porter, Sweet Stout (nitro), NB Surly Furious Clone, Petite Saison D'ete, Le Seigle Belge Saison, BM Cream of 3 Crops, Edworts Apfelwein
In Process: Braggot
Upcoming Brews: Surley Furious Clone, Uintah Wyld