I am also a member of that forum. I have posted alot on the knuckle ball there. Well, there are several grips, none of them incorrect, because you just want to find what works for you and then build on it. I throw the knuckleball and out of 10 mabey 7 of them break atleast a foot. I use the grip that is on my website. " It is in my signature. I have fooled around with alot of grips because some days your knuckler will break and somedays it won't and you will think it is your grip, but trust me, it's not your grip it is you.
Most people will recommend Charlie Hough's grip because it is "if thrown properly, which I find hard to do, supposed to be the best way to reduce spin. I just say you find a comfortable grip that seems to have potential and you will get the hang of it if you practice it enough.
I usually average 2 rotations or less on mine. I throw mine at aroung 55mph sometimes more or less. I think your grip, will limit the amount of velocity you will be able to put on the ball. I like to use a 4-seam grip and dig my nails into the horse shoe. You have to release it just right though or you will hook the ball. Alot of people say it is also not a good idea to put your thumb under a seam because it increases the chance of spin on the knuckler.
I think if you are serious. There is really no way to learn from someone else entirely. The k-ball is a unique pitch and everybody throws it differently. So the best way to lean is from experimenting, also taking and trying what may have worked for someone else. Just practice, untill you get consistant results that can progress. I have a couple of videos of the knuckle ball which everbody on this site has probably seen, but I will post one of them here for you to watch. Goodluck.
Also here is my website, I guess it wasn't in my signature. I use the first grip on there. The 4-seam one.