I have had a few people ask me about my scratch building, how I do it and what I use. I photographed the steps I went through to create the driver's side frame rail. Excuse the pictures, I'm having to re-learn how to take pictures with my camera, its been a few years since I've photographed model cars. Keep in mind, I had already created the passenger side rail before I started the drives side.
Masking tape used to create a template
Template transferred to plastic card stock and traced
Next, I roughly cut the shape with scissors. A little note about scissors, I don't normally use them, I typically scribe the lines with the back of a hobby knife to separate the parts. The problem with scissors is that they tend to "pull" as they cut and it is hard to keep them cutting in a straight line. However, since I was over sizing the part and tweaking to fit, it was fast and easy.
Once I had the general shape cut out, I tweaked the part and clamped it in place to be glued
Finally, you can see the near finished product on both sides, again, the pictures are blurry, but hopefully you can still see the seams from the different pieces of styrene that were used. Once I get all of my modifications done, I will use some putty to fill the seams and sand them down, follow with primer, and repeat until I'm happy with the end result.