Well, for resting (not hot holding for transport) you do let a butt or brisket drop in temp, otherwise it continues to cook. But several hours rest on a brisket or butt really helps them retain moistness and helps with the texture too.I must have missed the party on the cooler thing. People are resting their butts in coolers even though they arent trying to hold temp for a later serving?
A very nice resting cooler is the 24 can Party Stacker by Coleman. And as a bonus, the lid serves as a handy tray, and if you have the small Cambro, it fits between the handles.
That said, a Cambro is the choice for safely holding any event food... hot or cold. Here is the small one next to a table top roaster for scale.