Calling assist mid combo?

Hey newbie question

I see on combo vids or even on some missions that you have to call an assist in the middle of a combo?

How exactly is this done? Do you just have to use (S) after an air combo and then get your ally to hit him OTG? As far as I know you can’t call an assist while you’re hitting, getting hit or blocking, correct me if I’m wrong

You can call an assist when hitting, not when blocking.

One combo you can practice is with Arthur and Chun-Li with Lightning Legs assist. (y)
With Arthur on point do cr.:l:>cr.:m:>call chun>cr.:h:>qcf.:h:

With that combo, you’ll kind of get an idea on how assists play a role in mid-combo. Practice other combos you imagine and you’ll start seeing how you can sometimes delay assist calling so they can hit later in the combo, or so you can even continue blockstrings. Once you get this down you will even feel more comfortable calling assists actually.