Crud in the vent, how do I get it out?

Fashion a vacuum hose and stick it up the fresh air vents. You may have to "remove stuff" If you feel like pulling the front fenders, there are some little drain gizmos at the ends of the cowl cavity. Too bad, isn't it, that Mopar did not give us a removable grille panel there?
I opened up the vents and spun her up to 70. The stuff blows out. LMFAO! Open the doors, reach up inside and grab what you can. Vacuum out what you can. You might have to remove the vent assemblies to get up inside to blow it out with compressed air. Oh it leaves a mess but much better than the leaves holding on to the moisture after a rain or a wash. Bad for cowl rust.