I think I can help you the Rayden one. I didn't really have any difficulty with Cyrax and Frost's, but I think I actually spent two hours in a row trying to do Rayden's and I still didn't manage to pull it off. Here's what you do:
just push all the buttons on the controller without stopping. Dont wait till the fighting style is fully changed, dont wait till the kick is over, dont wait till the opponent falls to the ground, just keep pushing the buttons in the correct order and everything should be ok.

go at a normal speed through nan chuan, go really slow through jujutsu, and really fast through staff

With Cyrax your problem is the last three hits in sambo, am I right?

You have to do them very quickly, and your fingers need to be touching the direction buttons a split second before you hit the 2 or else it won't work.

However, Cyrax has better, more reliable combos too :).

With Frost and Raiden, the trick is simply to stay calm and maintain a regular speed (except, as has been suggested, in staff which should be quick). Make sure you're not pressing buttons too fast or too many times, and when you're style branching doesn't flow like it should try to tap CS multiple times quickly, it has helped me in the past.

Cheers,
Q

The problem is the controller-

with Cyrax you must push the fuckin buttons very quikly at sambo!