I used to season it, but the last 4 cooks or so I stopped rubbing the flat or the cap and haven't noticed a difference. In fact alot of people have commented that it taste better than usual. I was taught in my younger days it is all in the smoke and the wood you use for brisket.
I cook fat side up except for the one closest to the fire on my offset. The last two cooks I've noticed that the flat is a little dry on the one I put fat down. I am going to monitor it more closely next big cook, might need to just rotate it a little sooner.