Yo I don't have a video for ya, but I got so practiced, tried and true combos that should make it easier to use Haehyun. Also some additional info.
My belief is that finding hits that lead to 623 (K) 4 to j.k, j.p, j.s, j.hs into Fireball set up without spending meter will greatly improve every Kum player.
First is the effects of 623 (K) 4. It seems with Males characters you can land 623 (K) 4 (blue) twice on them if you hit them standing or after 2D. Females hurtboxes and weight are problematic cuz they hit the wall sooner than the males do so there hitstun time is shorten making it only possible to hit them once with 623 (K) 4 (blue).
Here are my findings.
Midscreen
2P/2K/2S, 2D, 623 (K) 4 to J.K, Double jump J.P, J.S, J.HS into Fireball set up
5K/6K/Cr.S/5HS(first hit), 623 (K) 4 to J.K, Double jump J.P, J.S, J.HS into Fireball set up
Corner
5K/CR.S/2P/2K/2S, 2D, 623 (K) to 5P, CR.S, J.P, J.S, J.HS into Fireball set up
These combos does not break the current gameplay with Haehyun which is to get the knockdown and lock them down with fireballs, but it does allow you to maximize the damage Haehyun can do without spending any resources.
My ideal playstyle with Haehyun is to apply constant pressure and force the opponent to FD or use other defensive choices to weaken and/or expose them. Trying not to go in too hard or close is the big challenge. I try to take advantage of the fact that Haehyun hits hard for almost anything that lands. I also believe Haehyun is NOT a 50/50 character however I do believe you can condition your opponent with fireball pressure. For example if you use my combo and do blue fireball set up. It can lead to a throw into a red fireball set up for another throw or use 6K or 412 (k) 4 to keep Haehyun plus and maintain pressure. Yes it is a 50/50, but I don't expect my opponent to get hit til they block only lows or highs at least 2-4 times. Haehyun ain't Millia since she hits like a truck so I usually win within 3-5 hits if I don't drop. Just using one of the two combos deals good damage for no resources used. This also allows you to save meter and get them to burst sooner cuz now they have more to worry about than YRC combos.
Also if you land 412 (k) 4 my combo works on the whole cast.
412 (K) 4, (have little time to dash forward if needed) 5K and/or/without Cr.S/F.S, into 623 (K) 4 (blue) to J.K, Double jump J.P, J.S, J.HS into Fireball set up. The 5K is used to properly line the opponent up for the follow up so it's ideal to be as close as possible to the opponent while their airborne. DO NOT RELY ON CR.S to set up the follow up merely use it after landing 5K.
I believe this should help everyone who may be struggling with Haehyun.