The thread will be helpful. You also don't have to read ALL of it, I did not. I love rayon, I use Sally's brand Graham Cellucotton, you can also buy it on Amazon. Just be sure you get the 100% rayon brand, there is "cellucotton" that looks almost identical, only it then lists "100% cotton),
I find rayon to be far more forgiving a wick than cotton as far as leakage and it plays to my strengths (overstuffing a coil, LOL) as it shrinks when wet. I found it absolutely stopped any leaking I had in its tracks, and not only that it lasts longer than cotton before needing rewicking, there is little rayon "taste" an it carries flavor well, and can withstand high wattage vaping well, if that's your thing.
But, I read some of the thread, posted a few questions, and got some great answers, and I was up and running with rayon fast, and I don't look back to cotton... ever. It's my favorite wicking material by far.
Best of luck,
Anna