This is way more accurate than that urban dictionary.
In Hawaii (depending on where you are) shaka is used all the time. Kinda like waving to someone with a hint of good vibe to it. Also to emphasize "hey that's cool". You see it a lot waving thanks to cars, too
To add to this, it's widely used in Brazil who copied it from surf culture.
China also uses it as part of their one hand counting system. To them it's the number 6 (pronounced 'leo'). The use of it in western culture has allowed them to adopt it as a way of saying something is cool. They will say 666 (pronounced "leo leo leo") while making the hand gesture to say something is cool. This fact was very fun to explain to my ultra conservative family back in the states.
Source: I taught in China for nine years in an international school with a very large Brazilian community.
Catholics are diverse, I suppose the Chinese ones might not be into the Apocalypse stuff that much, not everyone is. I don't really know, though, could be interesting.