From a relatively newbie that has done briskets that have all come out tender and juicy. I only buy full packers despite smoking in an MES 30. I simply cut it in half and have a flat half and a point half (I do not separate the point from the flat, the point half still has some flat to it). The packers I get (Costco) are untrimmed so you can trim as much or as little as you want I am fortunate that the Costco by me only sells USDA Prime briskets, so I personally can't say if the cut of meat matters. I cook without distirubing the brisket until it reaches 190F. Then I test for doneness using the toothpick test. Usually smoke around 235 using fruit wood of some sort.