Nice work there. I know now that my next suit base will include cardboard. It's cheap, can work with it like its foam, and come out with some amazing results.
great first attempt with bondo. you'll only get better at it. You made the rookie mistake of putting too much all over. (I did the same thing on my first master chief helmet a long while back. don't worry lol)
You recovered pretty decent though.
Just remember for next time
apply thin layers at a time in a specific area you want to work on at a time.
It really makes a huge difference.