623 D offer 77 frames which means around more than a second to continue attacking which means if done correctly there's no limit of 623D > 6C as long as you have the heat to do it.
dependings on what hit them first and what you follow up with, 623 B in the corner is possible still after 5-6 hits, except you hit them with an attack that has less than 90 p1 property
also if you do a fatal in the corner, just do the corner loop combo that's the most optimal thing to do....
if you hit them midscreen...
I have this combo which I usually do and it even can bring them all the way to the other corner
2C(FC)>6C>2D>5C>6C>dc(slight pause)>5C>6C>air combo>D musou > 6C > C musou
it will do around 4.6k with 25% heat. and this combo gains you around 40 something heat and you get good enough oki with ending it with C musou
the pause is needed so they won't be too high up in the air for you to hit them with the D musou