Back turned dread charged can only be reliably inputted when you jump over the opponent after an attack that leaves an opponent grounded. There were two attacks that allowed for decent setups with BT DC. That was after his 4B BE > iGDR and WR B > iGDR. You could also use 8 A+B but that relied too much on the opponent being an idiot. To do it you must input 9 G and 214 very very quickly after the iGDR. This would allow you to pull off strange shenanigans like BT DC K gun shot. This is the only way you can ever BT gun shot somebody that actually knows what they're doing *cough Signia, Blue, Zane cough*. Its also very very consistent compared to other methods others would suggest.
When you do 3K you input the mapped CE button as much as you can. Just keep pressing that button. Like 3-4 times is enough. This was my best method in pulling off BT B+K often. And yes, 4K K followed by the CE button 3-6 times.
