FRC is not easy for anyone.
It's just muscle memory and once again character specific. Some are easier than others.
Like let's take Ky for example. Throw FRC, HS stun edge FRC, D stun edge FRC
The throw one is fairly simple you press it soon as you see the slash in the throw hit
HS stun edge though has a funky delay on when it triggers so it could take a bit longer to learn.
D stun edge is really easy as well you just FRC when you see the ball form for the fireball
There are lots of little tricks you can teach yourself for FRC timing til it becomes second nature, by sounds or animations. It's one of those things where if you know how to practice it you can learn it quick, but if you are starting from scratch with no guide/tutor it's a pain in the ass.
Edit: But clearly I don't know anything about the game so what am I even saying!