rinse and soak Medium Toast French Oak cubes (2oz before soak) in Cognac (VS is probably the highest grade you want to go with here, just because of cost) in glass jar or other sealable container during entire primary fermentation step. Cubes may soak up enough cognac to lower level of liquid, add liquid to keep cubes completely submerged even though they will float.

When ready to introduce Cubes/chips to the secondary fermenter before racking your beer gently on top of them, remove them from the brandy and place them in a sanitized bowl. Discard or drink the brandy, up to you.

I'd start with 10 days on the cognac and oak. If you feel comfortable tasting without oxidizing from secondary, try it and see if the cognac and oak are coming through. If they've just started to come through, you can probably bottle/keg. Keep in mind that once you can taste the oak in the beer, even in a lighter beer style, it's easy to go overboard on it if you leave the wood in too long; sometimes it's best to pull the beer when you have the flavors rather than going overboard.

If you're having problems attenuating, do what I do, and add the sugar as a thick simple syrup with the cognac oak in secondary. You'll get a bit of a kreusen, but it shouldn't be so big that you'll need to worry about that extra head space, and the sugar should ferment out quickly.

I normally bottle and cork about 25% of this each batch just to see how the flavors develop over time with the slow oxidation of the cork.