Peter, I honestly think you're just not cooking enough, both in time and temp. I'm a big fan of water in the pan. I use it all the time for ribs. However, for brisket, I'm much in favor of cooking at 275+ and wrapping at some point in the cook. Since your issues are tenderness and dryness, I'd suggest trying foil once the brisket gets some bark. Like everyone says, cook it till it's feels like warm butter when probed in the thickest part of the flat. Open it up a while to lose it's steam, wrap back up and hold hot for a couple of hours, and then slice and enjoy.
Dave, if this had been one or two cooks I'd agree; but in this case it's about 8 in 10 that turn out dry. My usual process for low and slow is to let it go unmolested until my Stoker meat probe is in the upper 180s, which is where I set my alarm. Then, usually about a half hour later, I start to probe with my Thermapen.
When it's dry, the first few times I just figured it needed more time. So I left it on the next couple of smokes, checking for tender about every 20-30 minutes. It never happened. If I leave it on hoping to get tender, the flat will be 210-215 and the point will be 198-200 and good; the flat will be inedible unless sliced with a deli slicer and covered with sauce. I hadn't used water with the Stoker until this cook, hoping the evaporating water would add moisture. It didn't. I had excellent temperature control, too, and my temp probe from the Stoker was within 3 or 4 degrees of my recently-recalibrated Thermapen.
Note that I'm *not* judging 'done' by temp, just using it as a reference. There was no moisture whatsoever on the top side of the meat at any stage in the cook. Not even after butcher papering for 4 hours, after 9 hours in smoke. I've only experienced "warm butter" maybe 10 to 20% of the time, and that's in the thickest part of the point/flat--and when that's "like butter," the flat is more often than not, but not always, dry or both dry and crumbly (i.e. ovedone flat, nice point and point-over-flat).
As I have come to realize earlier in this thread, obviously I can't do briskets at home the way restaurant pitmasters do at Hill Country or Delaney's in NYC--I'd love to know why, but that's a different matter, and yes, I will start going to the Texas Crutch. My real goal is to learn the science of brisket cooking without that step, though. It's like it's a mission for me now or something
My next cook, I will go for about 12-13# trimmed, 250° until mahogany and a nice bark formed, and it's in the stall, then foil up with some beef broth and let it go for about 2 hours and see what happens, probing through the foil. Do I have the right of it or should I do something else?
And to do it without foil, but get perfect results....well, that's my new Holy Grail.