That's exactly how I've done the mask's Rich, it's not quite as easy as it looks but once you're away, it's fine.
The buxxer is the cost of the tool, plus you need an anvil, though you can improvise this, from a piece of inch plate or similar.
It's important to "set" the washer, as it locks the job together before actually riveting.
They might not look pretty but set properly, they will not part.
cheers
Steve