I've got some suggestions for that kind of a rusty look. Might want to practice on some cardboard first. Anyway here it goes, first a supply list.
Red/brown colored paint, desired body color paint, instant rust set, rustall, rubber cement, some fine wet/dry sandpaper.
First spray overall with the red/brown color which is rusty in color. After it has cured, take the rubber cement and spread it around the area's you want to stay rusted. Then lightly spray the body color, lay it on rather thin. Once dry, remove the rubber cement, and use the sandpaper very lightly to fog the edges of the rust/paint sections. If you want the deep rust and texture, then use the instant rust set next. A hint to make the instant rust set work better is to lay a thin layer of toilet paper or paper towell over that area, and use a paintbrush to dab on the rusting solution. Make sure it gets nice and wet, but not dripping. Keep it pressed down against the iron coating. This well help it to rust alot better with fewer applications of the rusting solution. After about 24-48 hours, pull it off and you should have a nice bright rusty finish. From there whether you used the instant rust set or not, brish several coats of the rustall over everything. Make sure you shake up the bottle ALOT, as it will help keep the rust particles suspended in the paint. Rustall can be airbrushed as well, quite effectively. Especially if you want a rainy rust look. I tend to use both. I also used the rustall in thin airbrushed coats to weather my Abrams tank.
To get that kind of flat tire look in that picture, the method will depend on what type of tire. If it's a hollow tire, then use my method, but put a spare wheel in the middle of the tire before you do the melting. If it's a solid tire, use the method used by the other guy. You can also use a dremel tool with a heavy grit sanding drum to sand cups and stuff into the corners of the tire where the sidewall meets the tread, and this will help make it look SEVERELY worn out. Broken or cracked windsheilds are also deceptively easy to model. If you want those tips let me know.
I've gleaned alot of this from years of reading scale auto and then expanding them with my own idea's. I've done alot of experimenting, and wasted alot of money on toasted kits, and wasted supplies, but I now have some good techniques. If you've ever seen me weather you know I tend to go a bit overboard. Which is probably what you are looking for with these wrecks.