To do a shinespark you actually need to jump in place while flashing - simply flashing isn't spinesharking (and if you jump while moving, you'll jump normally and conserve the charge)! So to recap: run to full speed, press "down" to conserve the charge, move to where you want/need to be, then stand still and press A/cross/whatever your jump key is to shinespark. You have a slight delay just before Samus launches into the shinespark to input the direction you want to go, so horizontal/vertical, and diagonal should be possible though I didn't try it here yet.
And if it works anything like Fusion/ZM did, if you shinespark and hit a slope, you'll start running again, allowing for multi run/charge segments. This is generally only used during 100% collection, but you never know, there might be devious tricks still lying ahead! (Just tested it, can confirm it works, as does all of the above, along with this: you can shinespark as the morph ball, too!)
So basically.... this:
http://gfycat.com/WaryFreeHomalocephale
EDIT: whoops, top of the page. Well, uh, I'm taking a break at about 2 hours in, and so far, this is everything I was hoping this would be. It's extremely faithful to the original (or my memory of it, but since I replayed it a couple of months ago, it's pretty fresh) and the additions feel completely in synch with what it was going for. I'm honestly surprised at the level of quality here.
