The ash in FL is pretty bad. Mine was covered on Friday when I drove home from work. I used a nozzle-less hose to try and just flood the junk off first, then went to a couple of buckets of cheap (read: under $4) suds that I poured over the car, then another rinse with a nozzle. That removed mostly all the pieces of ash and junk. Then I used the mitts, dried in a hurry and into the garage!
Join me in the raindance today.