ISO: Brinkmann Electric Smoker - HELP!!!

Brinkmann Electric Smoker:
OK I have tried this 3 times and have failed miserably. Someone help me please! David in Houston, can you let this Dallas girl know how your last attempt faired? Maybe that will demonstrate for me what is going wrong! During my 3 attempts, I tried a 3 lb brisket each time, tried foil, tried without, tried it for up to 9 hrs. STILL VERY TOUGH! I want that typical smoked brisket that you get at Spring Creek, Dickey's or the like that just shreds and the tug of a fork. But alas, no such luck for me! One thing I did use extension cord because I was trying to keep away from house and kids, maybe not enough power was getting to it??? But the meat thermometer read what it was supposed to according to Brinkmann owner's manual. So didnt think heat was the issue. Will try one more time with no extension cord. I did not open it too often. I used water in the pan up to the line. It never ran out. I used Hickory wood chunks not chips, kept away from element. We also cured smoker before hand. Was the brisket too thick? What cut of meat is best?, fat up or down? Too trim or not to trim? To wrap in foil or not, and if so at what point? I've heard some people have to smoke for 24 hrs. to get it tender...is this true???