Damn interesting art., Naz!
I'm thinking it could also be wooly adelgid poop, other insect poop, in addition
to the cannonball fungus; my wife's pos CR-V is parked outside 24/7, wherever
it is, and often under hemlocks at our house or, at the ball chasing track.
The black dots, regardless of origin, are a bitch to get off, even with clay.
The stuff one learns in school these days!
Decent winery right there: 6 Mile Creek Vineyard.
GL,mD