IAD's in VSav are executed rather easily with 9 9 or 9 (5) 6.
Only a few characters IAD's in the game though. Namely: Q-Bee, Zabel, and Lei-Lei. Although Jedah does have an air dash he also has a ground-to-air dash like Morrigan, making the act of IAD'ing kind of redundant. Basically because his airdash has startup whereas his ground-to-air dash has very little initial startup (none for the dash itself). It's by no coincidence that I play the three former characters (on and off) in addition to my interests in Felicia and Lillith.
Incidentally, all four airdashes are unique, with QB's being potentially the best out of them. Not just simply because it homes in on the opponent's location, but also because it will automatically turn her around if she is facing the wrong way. Whereas Zabel's does not turn him around regardless of relative position. And Lei-lei's always makes her turn the direction of the airdash, so backwards airdash causes her to face and attack backwards. Jedah, if you were wondering, also turns around automatically from his airdash or his ground-to-air dash once again making the airdash seemingly less useful, and he oddly doesn't have a backwards airdash even though he does have a backwards ground-to-air dash.
Pretty much the entire cast of VSav has a true command throw, barring Anakaris and Lilltih whose unblockable moves aren't standard (though they do both technically have unblockable grabs). While it's arguable if Jedah's dash into command throw is useful, it's pretty blatantly useful for the other three characters, particularly for Zabel and QB who have dash momentum on their dash normals. Empty airdash or airdash with a whiffed normal is obviously good QB and arguably pretty good for Zabel and Lei-lei, though Jedah certainly wouldn't be doing much of that off an airdash in lieu of just using his j.HK or some other tick setup.
In regards to their airdashes and ground dashes, Zabel can cancel both air and ground into an attack instantly. QB's ground dash has some substantial startup time before she can dash attack, but her air dash does not. Lei-lei is the opposite where she can cancel her ground dash at any time, but her air dash has a bit of startup before she can attack.
Implementing Lei-lei's and Zabel's airdashes is really very intuitive. Some trickery that Zabel has with his involves a backwards IAD (IABD) j.down+MP for a very fast overhead that spaces him in a way that is extremely difficult to anti-air or even see coming. He's also able to cancel his airdash into his j.down+kick moves which modify the drill trajectory, making them go pretty much almost downwards very swiftly. For Lei-lei, about the only thing out of the "ordinary" she can do is IABD toward an opponent that has tech rolled under her, since again her airdash turns her the direction she's "running". Though in Lei-lei's case she can combine and empty airdash with her Senpuubu chain-swing move, which is actually fairly common practice. Such as, air dp+HP, K to cancel, airdash, air DP+P, etc.
However, in some cases Lei-lei's Senpuubu chain swing alone provides better shenanigan potential that her airdash (even though her airdash it quite good). The reason being is she gets free-action after canceling it, and the move itself can pass through the opponent even while it's hitting. Thus, she's able to cancel it and attack in the air for a swift overhead, or land and do a low attack from either the left or the right side, all very quickly. But still, utility-wise, her IAD gets plenty of use. The Senpuubu cancel mixups; not-so-much, due to the slow startup speed for the Senpuubu and it's general flakey hitbox and the fact that it's basically guard reversal bait. Though that's not to say Senpuubu isn't used at all (it's actually frequently spammed as a standard practice).
Jedah's airdash does have one other unique property: it's an attack in and of itself. However, both his ground-to-air dash and his airdash trigger the special cancel properties for his air moves. In other words, during a normal jump Jedah is unable to cancel a jumping attack into a special move, but during either types of his dashes he is able to cancel and even whiff cancel his jump attacks into specials, allowing him to do things like j.MP into scythe.
Regarding the other characters, QB and Lei-lei are able to special cancel their light air attacks only during a normal jump, and QB can also cancel her j.mids too. They're unable to chain or special cancel during an airdash. Zabel isn't able to chain during his airdash either, but he can special/super cancel at a specific height from the ground during either his normal jump or airdash but (un)fortunately his typical IAD height is too low for any of his air specials or supers.
So, back to Q-Bee.. Some of the more devious things she can do with hers are actually fairly simple. Such as IAD'ing twice in a row, empty IAD'ing into a low, crossup/no-crossup IAD from left or right -- all of which can be done after a knockdown or reset or if you float past the opponent with her jump float. Other things she can do is upback IAD a good distance away so as to use the range on her j.LK or j.MK to your advantage. Or at the same distance, to empty IAD in an attempt to bait out a poke or other reaction from the opponent -- things like upback IAD then c.MP/MK or first upback IAD then forward IAD.
Once you get in, which is pretty easy with her, you can start ticking into IAD's and alternating with staggers. Such as staggering c.LK or staggering from c.LK to c.MP c.MK or going from c.LK to IAD, among other things. QB's crouching moves mostly hit low, only her c.MK and c.HP do not. Her c.LP and c.LK are also advantageous in terms of frames, but her c.MP is not, so when using c.MP as a lot it's a good idea to chain to c.MK. Also, chickenblock airdash is surprisingly good with QB, especially checkenblock into float and then airdash.
So just as a tl;dr list for QB:
- Crossup airdash
- Float airdash (crossup or not)
- Chickenblock airdash or chickenblock float airdash
- IAD * 2, namely: IAD then up/upback IAD
- Upback IAD midrange followed by a poke or IAD or even just walk-block
- Meaty left/right (front/back) IAD
- Reset/anti-air then airdash