Generally speaking... I'd argue 'yes'.
If you want your armour to come out looking like it just came up from Seongnam this morning, you'll need to put some effort into it. Unfortunately, that means biting the bullet and getting familiar with bondo and sandpaper. It's tedious, yes, and it's a pain in the posterior sometimes to get those details coming out just right - but. It's a learning experience you'll value highly if you ever decide to jump into other modelling/cosplay projects, and the extra effort you put into your work will truly set it apart from other costumes. For tiny details, I would abstain from using bondo, and instead get familiar with spot putty (which is great for those intricate areas) - but for the general mass of the helmet, bondo can't be beat. I might even go as far as to suggest experimenting with rondo instead - that will help you backfill those intricate details and preserve their shape from behind, so you don't risk losing the detail by exterior bondo work.
There are some absolutely fantastic guides out there, both here on the 405th and elsewhere, that will help you out tremendously when working with bondo and rondo.