Fat side up to 195, wrap in foil and rest in a cooler lined with towels for 1-3 hours. If you got your brisket from Sam's, it is probably Choice or Prime. So brining should be adequate. I'd recommend injecting for anything USDA Select for sure though.
I buy USDA Prime whole packer briskets from Costco ($2.79/lb), and I don't even brine or inject those (just rub), and they come out melt-in-your mouth floppy and delicious. Buying a flat/only can be a little dry, in that they can be over-trimmed. A lot of times with brisket, it's more about the quality of the meat (or how lazy and how much fat your particular animal had) vs the cooking technique in the SI.