The FG was 1.006 by the way. Anything special about the priming sugar vs DME vs something else? I have some cherry wine base in a can that I got at the LHBS. I intend to add to the cherry juice to a blend of the oak barrel batch and the glass batch and leave it in the barrel, but maybe I could use some for priming... Just don't know how to avoid gushers/bottle bombs. Any thoughts?
I like to add fruit (in whichever form) in bulk and allow any sugar to ferment out before packaging. If bottling, I am certain of the residual gravity going into the bottle, and I can adjust the priming sugar (or omit it entirely) based on FG. Its usually tough to figure fermentables from the info on the can. Also - any solids (skin, pulp, etc) will create nucleation sites in the bottle and cause gushing.
GREAT explanation of priming sugar calculations in this thread:https://www.homebrewersassociation.org/forum/index.php?topic=2177.0
Basically, Kai says every point of gravity added for priming equates to 0.5 volumes CO2.
If you assume brett will (eventually) work that 1.006 down to 1.000 in the bottle, you'll be left with 3 volumes of CO2, which is nice for Flanders. (I prefer it to be lower, but its completely up to you and your palate!)
Eventually is the key phrase there. Depending on cell count, storage conditions, and brett species, it may take 8-18 months for brett to finish off those last few gravity points. So, if you plan to hold on to these bottles for a year or more, I would just omit the priming sugar and allow brett to carbonate naturally.
If you want a few ready in a month or so, drop priming tabs into a few of the bottles and mark those "DRINK FIRST".
If you want a Gueuze/champagne-like carbonation, add priming tabs to get to 4.5 vol or so. With this much fizz, you'll want bottles that can handle the pressure and reduce nucleation points, so go with 750mL, punted, Cork n' Cage bottles.
If you don't know what you want, just try both!