If you wait until fermentation has completely stopped, then add sugar the same as you normally would for bottling, the same amount. If the gravity is stable and the Brett has gone through all the food possible, then the same amount of sugar you usually use will produce the same amount of...
I would not use the same equipment for sours as any other beer. I like to brew sours and other Brett beers but I do not use any equipment for 'normal' beers that have ever been used with Brett.
Maybe someone more knowledgable could explain why Brett is so resilient, but I have read many...