The flat and point cook at different speeds because the point has way more fat running through it, so it stays moist no matter what you do. What got me was the flat dries out from the bottom up when it sits too close to the heat source, even in an offset. Took me a while to realize I needed to rotate the brisket so the flat stays further from the firebox end. Once I started doing that the flat came out tender instead of that sawdust texture.