Ha this makes me glad I've always used the Y button.
It should be noted that it is possible to full shield without pressing down the digital part of the button, so if you get used to shielding like that (I have) WDing out of shield won't be a problem. (I only use the L button, and WDing out of the shield is no problem for me)
BUT you can't WD out of a POWERSHIELD really fast when you only use one trigger.... So yhea using both is better. (But I can't touch the R button b/c of how I hold the controller, my hands are to big for this game lol >.>)
Also it should be noted that using the c-stick all the time can slow you down unless you're using claw or the control stick to jump.
Which brings me to my next point: Almost everyone disagrees with me on this, but IMO people should use the control stick to jump more. Control stick to jump+c-stick for arial=Arial as soon out of the jump as you want. You can hold your thmb over the c-stick as you are jumping.
People say that you won't be able to go as far if you jump with control stick, but that is only true for full jumps and even then the difference is very small (if you do it right).
To do it "right", you press up/right or up/left (depending on which direction you're jumping in) and then you move it back to full right/left. If you did this fast enough you'll do a SH with the same amount of distance as a SH with X/Y. If you do the same movement slightly slower you'll do a fulljump with almost the same distance as a fulljump with X/Y (the difference is VERY small, with most chars you can't even see the differnce).
following DI with Uthrow Uair with fox becomes SO much easier this way.
just my 2 cents