I bought two cheap and slightly broken diecast cars from flea market and made PA-vehicles out of them. Since i'm not an car person, i have no clue what they are.
Not so much freedom as with plastic cars but still lots of fun to make. I used brake fluid with both of them to remove the original shiny black paint. With first one (skull markings) i tried different weathering techniques; hairspray, AK-liquid and sponge.
With second (biohazard markings) i used hairspray and salt, and i liked the result very much. So,if i recycle more of diecast toys, i will use that technique again.
I also used paperboard, cardboard and paper as usual.