Ideally the user wouldn't have to do anything. Whatever your editing tool is would have some "text blur" mode which functions and looks like normal blur but the end result is blurred garbage.
I think as far as culture goes it would be simpler to promote the idea that black bars are the only way to do it, than that you need to make sure you're using a special software that knows how to securely pixelate text.
It is a cool idea though, and text-shaped pixelation is much more satisfying than random noise. (And if someone's cheeky enough to decode it, they will be very disappointed ;)
