lol my graduation I used white shoe polish on the back windshield. it came in one of these handheld contraptions that had the buffer sponge on the front and you just squeeze some of the polish and spread it around. was hard as hell to get off if it got wet then clumped
There's car chalk made specially for writing on cars. It's what kids use at graduation time. Search for it online for a better idea.
lol my graduation I used white shoe polish on the back windshield. it came in one of these handheld contraptions that had the buffer sponge on the front and you just squeeze some of the polish and spread it around. was hard as hell to get off if it got wet then clumped