Well, first off: Welcome to SmashBoards!
I agree with you! If you don't have experience with Street Fighter it is like i can't even.. (I played Street Fighter once, but I still sucked)
I usually have to try it and fail a bazillion times in one match (which is certainly not helpful competitively)
I assume you know it's all the directions on half of your Circle Pad, from the direction behind your character (It swaps depending on which way they're facing) but assuming your Ryu is facing left: Left, Down-Left, Down, Down-Right, Right.
When I do pull it off, it looks like Ryu turns around for a split second on the Back input, then turns back around.
If you still can't do it (I don't blame you) just give up and use the regular Hadoken. The damage increase isn't totally mandatory, but the cool thing about the Shakunetse Hadoken is that it beats out other projectiles when the regular Hadoken can't, because it hits multiple times.
So that's my 2 cents. BTW, I use the 3DS version too. And I own the Wii U version. I am just in love with the New 3DS XL's Circle Pad. Nothing else compares!