Did a brisket this last weekend...only my second one ever.  I think I was on the right track until I let it sit too long.  Everything I've read is it's generally between 12-15 hours for a 15ish lbs brisket, so I started it at midnight.  It was done by about 2pm, so within the range.  I pulled it and let it sit until around 5pm.  It was a simple rub of salt, pepper and celery seed.  When I went to cut it, the outer layer was pretty tough and chewy, but the inside was pretty decent.  I want thoughts on that.  Then, I also want thoughts on what you guys do with left over brisket...We have a pound or two and I'm trying to figure out how to reheat it.  I'm thinking of making a gravy and making some mashed taters with brussel sprouts (one of my kids' favorites oddly enough).  Any other suggestions for brisket leftovers?