I was struggling with a dry brisket flat until I tried wrapping it in butcher paper with a half cup of beef tallow at the 160 degree stall. | BBQ Pitmasters - Hub Chatter
Honestly, wrapping with extra fat just feels like a band-aid to me. If a brisket flat is dry, it's usually cooked too hot or too fast. Adding tallow might make it seem juicier, but it's just coating a piece that got messed up. I'd rather focus on nailing the low temp and letting the meat's own fat do the work.