The whole thing is plastic bent around round items until the curve pleased me, the rest is glued pieces and LOTS of primer and sanding. It would be nice to have more advanced tools, but my space and budget keep me a file and sandpaper guy. If I don't like the way a part looks, I'll do it over until I do. I've wasted SO much plastic!
Some of the compund curves can be made with a super glue/ baby powder mixture. It's hard to sand, but very strong. I have never used putty, only this mixture. Much harder to work with than putty, but using it means the bodywork actually adds to the strength of the model body.