I messed with the trick a bit, and I'll record what kind of things you can do in 4-4 with Wing Kirby. But it's surprisingly easy to do on console (just mash 2 while condor heading into a waterfall and you'll fly). Here's what I know:
You can basically do whatever you want while in water, as long as you don't take damage. You don't have to continuously flap; you just have to be in "flap-mode". Furthermore, you can dive bomb inside waterfalls. And if you jump-cancel a dive bomb, you go back into "flap-mode," meaning your'e still flying underwater. Now, if you do a dive bomb to fling kirby out of the waterfall... you'll see once I get my video posted.
As far as I know, you can only do the wing-swim glitch off of a condor head. I haven't been able to do it out of a combo dive (haven't tested condor dive, but they're basically the same move). Maybe it's possible but frame-perfect (or very hard); after all, it's easy to do the condor head method on console because you can't jump cancel it (thus you can mash 2) unlike condor dive, which are jump-cancellable, and thus you can't mash 2. Metaknight can't condor head, he can only condor dive, but I'd imagine it works the same way. Furthermore, I don't know if Kirby can still ride MK while he condor dives (haven't really tried it); if he can't, then the point is moot.
Of course, I haven't tested Metaknight yet, nor have I done extensive testing (only about 10 minutes), so what I said about MK is just theory. I'll post a video of wing-kirby applications for level 4-4, as there are a few cool things you can do on console. I'm sure even cooler things can be done on TAS.
Anyways, if I find out that you CAN do the wing-swim glitch out of a combo/condor dive, AND that kirby can continuously ride on MK while he dives, then it can be very useful for water sections in TAS. Of course, assuming you can activate the glitch out of dives, then you'd have to test if it's possible to dive into the TOP of a body of water and activate it... which I don't know about. If it's possible, though, then that'd be HUGE, and would make world 3 so much faster... and would make my life hell for optimizing console any%.
And haha, Magtrollor is a better name XD But yeah, for the magolor fight, you can see my ideal console strat here:
http://www.youtube.com/watch?v=1zVunR-Of2o it's not perfect of course, just because it's so random, but it's very good.