I think that's why brisket is the challenge. Cook it low and slow to a high temp without drying it out! It is not forgiving, that's for sure.
I do mine at 250º to 275º. They don't dry out and I don't inject.
You need one that's fairly well marbled. That is where the juiciness comes from.
Actually, the Sam's Club here has just about the best briskets I have seen.