In regards to comboing into j2c, the only worthwhile time to it is at the end of your air combo, if you are in the corner. This allows for a techtrap that you can exploit by doing a 5c as soon as you land, and if they fail to tech the first bounce, or just plain don't want to risk getting reset, you can catch them with 2c and follow that up with 22c to have a solid knockdown and a pit on them.
As for instant j2c, it isn't something you can watch in videos and say "Dang, I wish I could do that". It is an absolutely essential weapon for akiha, because without it, all you have is advantage on block and tick throws. Lows cary a lot more weight when there's something like j2c that you need to be on the look out for. The easiest setup to practice if you want to take some steps towards mastering the hardest and yet most essential trick to the top tier Akiha, is getting your opponent to block a tk 236a and then immediately throwing it out there. As for practicing fomboing off the hit, you can practice the timing on landing the 2b after it by doing ja > j2c > 2b(if you can't get the instant j2c consistantly enough to use it in matches). using a healthy mix of ja > jb and ja > j2c will make your ja much more threatening, and then of course you can always land and throw. Also, I wouldn't really expect to be getting 50% life combos off the overhead, but it still carries probably the biggest combos off a command overhead in the game. Also, remember you can't jumpcancel your attacks on block, so you need to wait a it after 2a if youw ant to throw out the overhead. I don't really advise doing it outside of tk flametounge games unless you're really inside your opponent's head and you know it will hit.
B pillar(214b) does marvels on block, and at the end of blockstrings ever so often to bait CH(not too often, because if your opponent is looking for it, it's easy to see Akiha assume the pillar position). Off a b pillar CH you can catch with 2c and then launch into an air combo off a charged 5bb. To time the catch so that you have time to charge the 5b, try to 2c them with the top half of your sweep. on block, it's pretty much the same as a blocked tk 236a, and so you can either run in and mixup or throw out a tk 236a and mixup off that/collect your free combo.
Comboing into 623b is fairly easy. Off any 2c, just wait a few frames for the input and it will hit like magic. Great for collecting a *solid* knock down and dragging your opponent to the corner. Over the next couple weeks I'm going to be putting some time towards learning her wacky corner stuff, so hopefully I can demystify that area of Akiha for the nonjapanese players.
Oki game that was not mentioned in the previous post:
Meaty 5c: Great for starting block strings, and if you feel a low shield comming from your opponent(as dumb as it sounds, it happens all the time, and the japs eat 5c all the time on wake up). This also works to catch jumpers, but it will wallslam them and is not the ideal counter if you think they are going to jump. 4c will do the same job as 5c, but it is slower and more vulnerable, but is also much much better for catching jumpers, because you can combo off of it midscreen. Beating wakeup jump is very important for Akiha because if you whore the ribbons, your opponent will figure out how jumping is the only way out of that trap, and will find them selves dping/jumping a lot. Perfect meaties also destroy sloppy reversals, so that's an added plus.
Meaty 2b: Only one use: beating mid shield. This is important because a lot of people, if they chose to wakeup shield, will shield mid, because it shields all mid/high attacks as well as 2a, which is Akiha's staple low poke. A nice way to get sneaky.
Arcdrive/Throw: It's a fairly lowlevel tactic, but it works suprisingly weel if you're not meaty arcdriving every time you find your self in max(like I did back when I first learned of the glory of the oki arcdrive). Punishes heat brilliantly. Punishes backdash(another good method to get away from an angry Akiha). And of course, punishes shield or block even better, because you basically reset your oki and get almost the damage of a midscreen bnb. I again want to stress that you can't let your self get predictable on this, because if they jump, it's a free combo for them. Also take into consideration that after the full invulnerability from waking up, there is a slightly longer period of throw invulnerablity, so the timing on a meaty throw is slightly off from a meaty hit.
Jump and do a 236a right over them as they're waking up: I don't know why, but I have a huge successrate with this tactic. You time it at the latest possible second, and maybe aim to cross them up but just barely. It hits the guys at my local arcade, and the guys at the tournies, and I have no clue why.
The only other real trick the previous poster forgot to mention was like, the super jump tk ribbon, which is good for getting a meaty ribbon on them after an airthrow and putting your self in range to overhead after, as well as if closer, you can use it to cross up much more quickly and easily than with the regular forward tk ribbon.
As for solid pokes, 2a, 2b, and 5b should be your main pokes of choice, doing short guard strings to stay on top of your opponent to keep pressure on, and looking for an opening to get a ribbon or pillar on them. 214b/a also work well as preemptive anti air, especially because they are not air blockable, and give juicy ch combos. 5c and 2c will also give you damage occasionally as pokes, but I wouldn't try to religiously poke with 5c or anything. It's just too unwieldy. And if you start overusing 2c as a poke, not only will your combos deal crappy damage, but you will also start using it inappropriately and most likely be punished for it. Also, remember most 2a's can be turned into throws on block, as long as you don't whore it. AND PLEASE, don't do 2abc5a as your blockstring.
Basically, as akiha you don't win off massage combos, you win off controlling your opponents options and making openings for your self. You need to get them afraid of you. Besides that, just remember that when fighting against Sion, if she see's your b pillar comming and is not in blockstun, she can eat it wth 2c, cancel into 214c, and get a free combo. Use b pillar wisely.