I am a fan of hot and fast cooking of brisket now. For me that means 270F to 300F (choose a specific temp, I don't mean cook in a range). I would think you have a 6lb flat, so you are looking at 3 to 4 hours, maybe 5 at the lower range of temps. I use a remote to see temperatures and start to check around 195F. It goes pretty fast with just a flat. I use a thermometer probe, not the one in the meat, to poke and see if it goes in real easy.
I'm feeling bearish, and I'm packing a Wusthof Grand Brisket slicer from MABA
Whip It Off, Chambers!
"perhaps...but then again...maybe not..."