We printed black and white photos of the vehicle, put chalk pastel on the back and traced over the outlines to transfer it to the scratchboard surface and they used 'pen and ink' techniques to create the different values. They turned out great, as you can imagine (I put a few at the bottom of this post) because we were basically tracing all the hard stuff.
This year, I wanted to teach them the grid drawing method a little earlier in the year so they could use it to draw things later, if it helps them....so we selected an image of a vehicle and grid drew it on white paper. Then, we used ball point pens to create the values.
I used the paper mate ink joy ball point pens in black because they fit into my budget and I ordered them on amazon at the last minute, but there are a lot of great pens out there that would work.
Here is the slide show I used to introduce the project with some more examples.