Tim, I feel for you, as I do not have an airbrush either. Most GAZ models I have seen have a red star on the sides. You may be able to find an appropriate sized one from a 144 scale russian aircraft decal sheet if you do not want to paint a couple on.
Here is a bit more work I have done on my 1/48 Wespe resin Fiat 508. I worked on the interior, including the dashboard and seats. I installed the gear shift (a kit provided straight pin which you have to cut down) and added hand brake from scratch. I got the base coloring and pin washes done for the most part. You can see I still need to work on the windshield frame when these were taken after a weekend of activity:
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A couple of nights ago I carefully trimmed the flash form the inside of the windshield frame, cut the "glass" from the thin clear plastic provided in the kit, and carefully fit it into the frame using "Tacky" craft glue. I also made and added a windshield wiper and small motor box from scratch.
I also made a rough stencil for the ram's head door markings. Last night I used a black permanent ink felt tip pen to get the basic stencil down, and then finished it up with thinned black acrylic craft paint using a 20/0 Windsor & Newton brush. Here it is with the door markings and windshield added:
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Next step: adding the wheels, headlight lenses, canvas top and then give it a good dusting. Any comments welcome.
Jim