Some info since this place is lacking (Marn you seem perfect to give us info, what with 1st place and all 
):
With Yun your main footsie tool is the target combo st.mp to st.fp, if they connect you combo into back.fp. Two hit-confirm so should be plenty for you to see before going into last hit since if they block it you’ll be punished bad. St.mp does wonders vs. Ryu’s new nerfed crouch medium kick, you can catch him on recovery and punish him. However if your opponent has a footsie that is out of range of st.mp (eg. Evil Ryu’s cr.mk reaches FAR but has poor recovery) your aim is to stay at the max end of that range, and when it’s thrown out instead of trying to poke it, neutral jump and HK dive as early as possible. You can catch them on recovery and combo, and even if you didn’t hit it’s hard to react to a dive at this range.
Best anti-air hands down is LK dragon kick, MK and HK tend to trade, while LK rarely ever trades.
Always crouch tech when dive kicking, no matter what, since your enemy is going to try to mash throw or something stupid. And after you dive and it’s blocked, take a quick step back and do something like crouch tech cr.mp or cr.lk, this allows you to block reversals and frame trap them.
Yun’s cr.lk makes him crouch, nice to use on stuff like Guy’s wakeup to make his EX Hurricane whiff, and other characters on which this works on.
Learn Yun’s dirty dive that avoids/stuffs SRK, best example is in the Kindevu vs. Jobin video to learn.
If opponent tries to cross you up, HK Dragon Kick to safety, since it goes far and whiffs. If in front of you and trying to bait you by standing, just block, since standing means you can be punished more which some opponents will try to do in anticipation of it.
Command grab on wake-up is a nice mixup. Also has great range, so after one cr.mp do it, or do the Marn grab where two cr.mp, then st.mp cancel into fake palm into command grab. Be careful of backdash and reversals or a jump, Yun’s recovery on this is huge. And f+mk (overhead) after three cr.lk or two st.mp to avoid being hit by their crouch tech, or on wakeup.
To avoid blocking a dive some opponents like to neutral jump, instead of anti-airing it due to its unpredictable nature on the player. Many times you’ll land before opponent, start getting used to LK Dragon Kick on their descent. cl.MK sometimes works but will be stuffed on descent due to not enough time for it to be active, and you’ll be counter-hit, best option is LK Dragon Kick due to invincibility. cl.MK has its use if opponents try to jump at a close range that leads to cross-up, you can jump and dive, but I prefer to combo into MP Lunge due to damage + meter building + knockdown. It’s the best anti-air in this situation, and most damaging. Can lead to Genei-Jin if you have the meter, but haven’t experimented going into combo (most likely with LP Lunge into whatever).
Genei-Jin, don’t know the optimal combo, but I’m doing the Dragon Kick loop. Bonus is that it can be done from mid-screen, and great damage.
(Mid-Screen Opponent on Ground): Genei-Jin Activation, st.HK, LP Lunge, st.MP (Opponent will be a bit far and at this range for MK far version will come out which doesn’t launch, on some characters needs timing, or doesn’t work) HK Dragon Kick, cl.MK HK Dragon Kick loop, finish with cl.MK jump Dive Kick Reset.
That’s all I have for now, hope it helps.
