The Mongean shuffle sounds interesting, though time consuming. I might try it, though.
Currently, I riffle. Overhand shuffling doesn't give me the amount of randomness I'd like and scrambling just seems inconvenient.
Yeah, the wikipedia article has some interesting information on randomness. Apparently the overhand is a terrible way to mix the cards if you want them truly mixed. One math site said it takes 2500 overhand shuffles to randomize a 52-card deck.
And, yes, my doing the Mongean is a little slower than the others, but I actually can do it relatively fast now.
I would love to see videos of people rifflling tarot cards, as it seems to be quite popular. I'm wondering what I'm doing wrong. I seem to end up mashing the cards together, and have ended up peeling the front from the back of some cards, or making other kinds of dents and rips.