First brisket ever question

I haven't tried that.

Can you double wrap it in foil with a little AJ or beef broth and leave the smoker run at 140 or lower?

run up to the local 7-11 , gas station, grocery store etc and grab a cheapo styrofoam cooler.

What's the current temp?

If you can hold it at 140-150, follow Arnies' advice. Otherwise I'm afraid you'll have to refrigerate it even if it's not up to temp. You can re-heat it if need be.

Buy an Igloo on the way home

Good luck!

Good call Coach!

Wrap the brisket in foil, then wrap it in a towel, then wrap it with plastic wrap, lastly wrap it with a blanket and put it in a cardboard box. What you re looking for is layers of insulation to retain moisture and heat without leakage ruining the blanket.

As suggested layers are the key.Sleeping bags were the trick at cookoffs for years.Don't know about your temps there today,but well wrapped,in your sealed car in the bright sun could yield safe holding temps for the afternoon.