How do I clean this gunk!

In the good ol days we would take them to the car wash. Their high pressure sprayer would get'er done. According to EPA we aren't supposed to do this at home if the run off can go to ground water, and better not get caught at the car wash.
I use a screw driver and compressed air to break up and remove the majority, then oven cleaner, then high pressure rinse, then brake parts aerosol, then paint.