What I do is trace original artwork onto tracing paper (or even oven baking paper is fine)
Then tape that to cardboard , go over the tracing with a pen to get an indentation on the cardboard , remove tracing paper , go over  indent with pencil/pen .
Then cut out shapes for 1 colour .

Rinse and repeat above to make stencil for second colour .
Also have alignment marks to be able to align correctly against cab .