Vacuum Forming

how difficult would this process be, create armor out of cardstock, resin, bondo to add details, once piece completed vacuum form?

also on the bondoing what is the process for that. do i just put the bondo on then go back with an exacto knife for details, or do i try to follow the form and make detail with the bondo.

You'd have to use a dremel to sand the bondo, you can't exactly cut it.