Thanks for all the help and suggestions, guys. I finally understand these run cancels. I'm no expert at them but I messed around with Scorpion's Hellfire a few weeks back and that actually helped me with Johnny Cage's A-List run cancels. It's all about muscle memory and putting in some time. I'm not very good with fighting games so it took me about 30 minutes to really get it down.
The way I learn these things is by chopping the combos up to small parts. Get the small parts down and then start linking them together. I'm sure there are gods on this board that can do this stuff in their sleep but for all the other mere mortals like me this is how I did it.
A real easy one is:
b34, bf hold 4 and run cancel, 21, bd3
From there you can meter burn the bd3 or I believe you can extend the combo when the opponent is stunned. I happen to use an arcade stick so I don't know how much that affects the learning curve for this stuff.
At the beginning I practiced b34 bf4 first to make sure that glow kick comes out. Then I practiced holding the 4 and then releasing it. The trick with the run cancel is holding the 4 and letting the joystick return to the neutral position and then tapping forward twice and hitting the block button to run. If you do it right you'll see Johnny Cage hold the glow kick for a fraction of a second and then run. You'll know you got it perfect when Cage doesn't even go into the hold animation and pretty much just runs forward.
After getting all that down then you can link whatever combo you want into the cancel. The thing is you gotta do it quick. I like 21 best only because the block button is right after my 1 and 2 buttons so I pretty much just hit block21 with my ring, middle, and fore fingers respectively in a quick piano like motion.
Like I said, this is just a start for me and this is how I learned it. Hopefully this can help someone here. This combo is just the start of a whole new world of combos I can start to learn.