Using photos to build a model as a “wreck” is very helpful, understanding how metal folds on impact is key to making a realistic job. I use heat from the inside of the model first (frame, rad cradle, etc.) to get things started, doing the hood and fenders last.
But before I start, I determine what type of wack its going to be so that I can map out what I want to cave in first. It’s crucial to cut open the fender from the door, poke out head lights, remove any trim using a razor and finally making scratches where I think the paint would scraped, Video sample below.