Every post in here has been helpful, thanks very much guys!
I’ve only gotten a chance to practice the Fei Long rekkas (I don’t own any systems besides NDS), and after some practicing, I’ve found a good method to get it everytime, while also allowing the delay needed for hit-confirm purposes.
At first, I tried finding the fastest way of doing it, but my execution didn’t have the consistency to reliably find the exact speed. So instead, I went for the slowest way to connect them.
My first error was trying to combo a c.lp into a fierce rekka as fast as possible; I was literally plinking the buttons (lp~hp) because I thought that would be the best way to guarantee that the rekka comes out as a cancel. As it turns out, speed isn’t necessary, and is actually a mistake, as that was probably the major cause of my rekka problems. Doing it that fast was just no good. So I delayed it a bit, as I would a c.mk xx hadouken. That fixed that problem.
The next part was getting the 2nd and 3rd rekka to hit. The method I finally found was to press the HP for the 2nd rekka right after I heard the sound of the first rekka hitting. I figure this method wouldn’t work well in noisy environments, so I made sure to practice that method enough to make it muscle memory. Now I have it! The benefit to this method is that it allows you to see whether or not the rekka comboed, making this a hit-confirm combo.
Hopefully I will get a chance to see if this method translates over to Iori in CvS2. Thanks again!