So you're playing on a game pad? Then you're like me. I never learned to pick up a fighting stick even though I used them a lot in arcades. Something about using a stick at home just never felt the same. Anyway.
Honestly, button inputs for chain-throws are a lot easier with an arcade stick. But we're using a pad. For King's chain throws I use 80% teaching my thumb how to hit all the buttons it needs to and 20% programming the shoulder buttons to handle those inputs that my thumb would really struggle to get all back to back. Like 1&2 to 1&4 to 4&3 to 2&3 to 1&2&3. Those are tricky to hit consistently with just my thumb, so I intersperse the shoulder button inputs.
Also, do you know what button buffering is? It's a very important skill for Tekken. I don't mean to sound smug or anything, but I'm always surprised at the people who don't know what it is. I'm an old gamer, so I come from a time when I had to figure this crap out on my own, with no internets. So I always ask stuff to make sure other gamers know too.
Obviously, the same thing is applicable to Nina/Bruce. I spent literally hours in practice mode for Tekken 3 learning which chain throws could be used to counter whiffed moves and just being consistent with them.
It's not enough to know the throws, they're hard to land. So it requires match-up knowledge to know when and where you can land them.
Which is why I struggle more against new characters, because I don't know anything about them. Although, I'm also just really not playing at the level I used to when I had time to really waste playing the game all day.