Here are a few wrecks from my collection: They may inspire you, or, failing that, provide you with cover in a firefight.
The mercedes is a 1:43 Mercedes Mampe by Burago. It was missing its wheels, so I was inspired to do a completely stripped version.
I removed the windows, doors, steering wheel & seats, then drilled a few (but not too many) bullet holes. I then glued the model to some brick supports made from sprue.
I sprayed it black and drybrushed it with dark brown metal, followed by a dark metal colour. I painted some details and some rust and finished it off with lots of graffiti in white and red.
These are three models which I smashed up as a kid many years ago, I found them on my parents' attic and decided to paint them up as wrecks. On the left is a Hot Wheels Volvo, in the middle a Solido BMW M1 and to the right is a Norev CitroŽn 2CV6.
The CitroŽn was missing its roof and hood, so I made a new roof out of thin cardboard. I painted it in a dirty blue, with a lighter drybrush, the roof and interior were painted dark grey, and details were painted silver. It was dirtied up with brown wash, and the front (where the engine should be) was darkened with some black wash and drybrushed metal.
I wanted to do a completely burnt out wreck, so chose a car with doors that could open (and thus be removed), and with tyres that could come off, both are not a given with most car models.
I took a 1:43 Hongwell/Cararama Mercedes Benz M-class. First I gave the model a serious beating with a hammer, removed (and beat) one of the doors, and removed the tyres, windows and some of the plastic details.
Then I bent the axles so all wheels were level with the bottom of the car and drilled some bullet holes. I glued the roof railings, bumpers, and separate door.back onto the model, adding a plastic skeleton in the driver's seat.
I sprayed the whole model black, painted it dark brown and gave it a light black drybrush, followed by a metal drybrush. The interior and skeleton were picked out in grey, the bumpers in black, and the bullet holes in silver.
This is a 1:43 Hongwell/Cararama Alfa Romeo 166. Again I beat it carefully with a hammer (too much and the passenger compartment will just collapse, which makes it look wrecked, but not shot-up), removed the windows and drilled lots of bullet holes.
I also melted/flattened the (rubber) tyres, which didn't go as well as with the completely plastic wheels. I painted it in metal and then in Tamiya metallic blue, and gave the bullet holes the same treatment as above. The bullet holes are rather large (drilled with a 1.5mm bit), but I kinda liked it that way.